Chapter LX: Part 2 (21)

When the article requires renovation as well as scouring, it is placed, whilst still damp, on a board, and the threadbare parts are rubbed with a half-worn hatter’s card filled with flocks, or with a teasel, or a prickly thistle, until a nap is raised; it is next hung up to dry, after which it is ‘finished off’ as before. When the cloth is much faded, it is usual to give it a ‘dip,’ as it is called, or to pass it through a dye bath to freshen up the colour. BLACK and DARK BLUE CLOTH, if rusty or faded, is commonly treated to a coat of ‘reviver,’ instead of being ‘re-dipped,’ and is then hung up until next day, before being pressed and finished off. See SPOTS and STAINS.

=SCOURING IN ANIMALS.= See DIARRHŒA.

=SCOURING DROPS.= See DROPS.

=SCROFULA.= _Syn._ KING’S EVIL, STRUMA, STRUMOUS DISEASE. By modern pathologists scrofula is regarded as a constitutional tendency to form and deposit in various tissues and organs of the body a substance called _tubercle_.[148] The _tendency_ may, however, in some cases only exist without any actual tuberculous deposit taking place. Sir James Paget thus describes scrofula as generally understood to be a “state of constitution distinguished in some measure by peculiarities of appearance even during health, but much more by peculiar liability to certain diseases, including pulmonary phthisis. The chief of these ‘scrofulous’ diseases are various swellings of the lymphatic glands, arising from causes which would be inadequate to produce them in healthy persons.

[Footnote 148: See Phthisis.]

“The swellings are due sometimes to mere enlargement, as from an increase of natural structure, sometimes to chronic inflammation, sometimes to an acute inflammation or abscess, sometimes to tuberculous disease of the glands.

“But besides these it is usual to reckon as ‘scrofulous’ affections certain chronic inflammations of the joints; slowly progressive carious inflammations of bones; chronic and frequent ulcers of the cornea; ophthalmia attended with extreme intolerance of light, but with little, if any, of the ordinary consequences of inflammation; frequent chronic abscesses; pustules or other cutaneous eruptions frequently appearing upon slight affection of the health or local irritation; habitual swelling and catarrh of the mucous membrane of the nose; habitual swelling of the upper lip.”

Scrofula is a disease which almost always shows itself during childhood, and rarely after maturity has been attained.

Scrofulous children, or those of scrofulous diathesis, are frequently narrow-chested, or their chests present that projecting appearance known as ‘pigeon-breasted,’ their abdomens are also unnaturally large, and their limbs emaciated. Their circulation is languid, and they are very generally attacked with chilblains during inclement weather. They also suffer from obstinate indigestion. Bearing in mind the fact that scrofula is frequently induced, irrespective of hereditary taint, in the children of the poor by bad and damp air, insufficient food and clothing, exclusion from sunshine, and such like insanitary surroundings, the chief treatment that will suggest itself will consist in remedying these adverse conditions. Hence the patient should live on generous but digestible food, partaking of meat twice a day. Milk and eggs also form an excellent diet for the scrofulous. A scrofulous mother should refrain from suckling her offspring, and procure a wet-nurse for that purpose. Flannel should be worn both summer and winter. Various medicines have been employed in this disease, including cod-liver oil, sarsaparilla, bark, syrup of iodide of iron, the alkalies, and mineral acids. Of these cod-liver oil and syrup of iodide of iron deservedly enjoy the highest reputation.

=SCUDAMORE’S LOTION.= See LOTION, GOUT.

=SCURF.= _Syn._ FURFURA. Scurf “is a natural and healthy formation, and though it may be kept from accumulating, it cannot be prevented. It is produced on every part of the body where hair is found, although, from the more active growth of hair on the scalp, the facilities for collecting, and the contrast of colour, it strikes the eye most disagreeably in that situation. This will show how futile any attempt must be which shall have for its object to prevent the formation of the scurf. It may be removed, and should be removed, every day, with the hair-brush; but prevention is impossible, inasmuch as it is opposed to a law of nature. Occasionally, as a morbid action, an unusual quantity of scurf is produced, in which case medical means may be adopted to bring the scalp into a more healthful state.” (Eras. Wilson.) In such cases the daily use of some mild stimulating or detergent wash, with due attention to the stomach and bowels, will generally abate this annoyance.

=SCURF POWDER——Grindpulver= (Mahon, Paris). Three powders which, according to Chevalier and Figuier, are nothing but wood ashes. Buchner found no alkalies, but announced the following composition:——Organic calcium carbonate (oyster shells, egg shells, crab shells), with a little gypsum, charcoal powder, and more or less brick-dust, powdered, mixed, and exposed to a moderate red heat in a covered crucible, till part of the chalk is converted into quicklime, and the gypsum reduced by the charcoal powder to calcium sulphide, which in its turn is gradually converted by the air into calcium sulphite. All three powders are made of the same ingredients, but in different proportions. No. 1 has more gypsum and charcoal powder; No. 2 less charcoal and more chalk; and No. 3 more brickdust. (Wittstein.)

=SCURF SALVE——Grinsalbe.= In France it is generally a mixture of 2 parts slaked lime, 5 parts soda crystals, and 25 parts fat. (Hager.)

=SCUR′VY.= _Syn._ SCORBUTUS, L. This disease commences with indolence, sallow looks, debility, and loss of spirits; the gums become sore and spongy, the teeth loose, and the breath fetid; the legs swell, eruptions appear on different parts of the body, and, at length, the patient sinks under general emaciation, diarrhœa, and hæmorrhages.

The treatment of ordinary cases of this disease mainly consists in employing a diet of fresh animal and green vegetable food, with mild ale, beer, or lemonade, as beverages; scrupulously avoiding salted and dried meat. The fresh-squeezed juice of lemons is, perhaps, of all other substances, the most powerful remedy in this disease in its early stages, and is useful in all of them. Effervescing draughts formed with the bicarbonate of potassa (not soda) are also excellent.

In former years, before the nature of this malady had been intelligently investigated, and the proper preventive methods and remedial measures for combating it were unknown, scurvy was not only a very common but a very fatal disease in our own navy, as well as in the navies of other powers. Of 961 men who constituted Anson’s fleet sent out during our war with Spain in 1742, 626 died of scurvy in nine months; whilst Sir Gilbert Blane records that in the year 1780, out of a fleet composed of between 7000 and 8000 men, more than 1000, or one in seven, perished from the same cause. Sir Richard Hawkins, one of the naval celebrities of Elizabeth and James’ reign, affirmed that daring twenty years he had known 20,000 sailors fall victims to scurvy alone; and a Portuguese writer, quoted by Sir Charles Blane, speaking of the number of victims from scurvy, during a naval exploring expedition of his own country men, says “that if the dead who from this cause had been thrown overboard between the coast of Guinea and the Cape of Good Hope, and between that Cape and Mozambique, could have had tombstones placed for them, each on the spot where he sank, the whole way would have appeared one continued cemetery.”[149]

[Footnote 149: Dr Guy.]

The statistical report of the navy for 1871 offers a gratifying contrast to the above figures. From this document it appears that out of a total force of 4720 sailors, only four were affected with scurvy during that year. The much greater number of men attacked by the disease on board merchant ships appears to be due to the inferior or worthless character of the lime or lemon juice purchased by them.

Writing on the hygienic condition of the merchant marine in 1867, Mr Harry Leach says:——

“We are prepared to maintain, from the following table (and other statistics from which these have been taken), that the want of good lime or lemon juice was distinctly the cause of scurvy in the vessels below mentioned.

No. of Hands Cases of Result of examination
Name of Ship. (all told). Scurvy. of Lime juice.

Hermione 17 5 Sulphuric acid.
Merrie England 29 10 Stinking.
Stirling Castle 32 6 Very weak.
Hoang-Ho 21 5 Acetic acid.
Blanche Moore 35 8 Musty and nauseous.
St Andrew’s Castle 19 7 Citric acid.
Tamerlane 21 4 Nauseous.
Marlborough 23 8 Very weak.
Galloway 29 6 Short allowance.
Tamar 17 2 Very weak.
French Empire 27 7 or 8 Citric acid.
Eaglet 14 3 Thick and nasty.
Geelong 14 9 Taken irregularly.
Thorndean 35 2 Spoiled (short supply of
provisions).

Taken with ships that, with others, have arrived in the port of London during the past two years with cases of scurvy.

“Of direct causes this is undoubtedly first and foremost; but of indirect causes we have a few words to say. Dirt, bad provisions, and any form of disease to which sailors, in common with other men, are subject, will predispose to scurvy. This cannot and should not be denied, but it affords to parsimonious captains a very large peg whereon to hang sundry invectives as to the cry lately made about the continued prevalence of this disease in the mercantile marine. Such captains, with pardonable ignorance, consider scurvy a form of venereal disease, give the wretched subject thereof mercury, and bring him into port salivated as well as scorbutic.”

Mr Leach further adds:——

“In summing up statistics of scurvy for the past year (1867), we find that a total of 235 accredited cases were admitted into British hospitals, giving no account of those who convalesced in sailors’ homes or elsewhere.

“To this we may add, that seven sailors were left at St Helena, from a ship recently arrived in the Thames; that a vessel put into Falmouth on the 29th ult., with no less than sixteen severe cases of scurvy on board, and that between twenty and thirty cases have arrived in this port during the present month. It would be well (as a supplementary aid to the prevention of scurvy by inspection of lime juice) that the dues levied for the St Helena Hospital should be abolished. It was stated to us some weeks ago by a very old inhabitant of that Island, that this fact alone caused many ships to pass without calling for needful supplies of antiscorbutic material.

“I would however remark, that if the system proposed by the Seamen’s Hospital Society were put in force, no such aid to the prevention of this disease would be required, inasmuch as every ship would then be supplied with good lime juice.”

The following figures, giving the number of patients suffering from scurvy admitted into the Seamen’s Hospital, shows a decrease in the disease, since the publication of the above:——

In 1865, from British vessels, 101; foreign do. 1
” 1866 ” ” 96 ” 5
” 1867 ” ” 90 ” 4
” 1868 ” ” 64 ” 10
” 1869 ” ” 31 ” 9
” 1870 ” ” 30 ” 21
” 1871 ” ” 24 ” 16

=SEAL′ING WAX.= See WAX.

=SEA SICKNESS.= The most effectual preventive of sea sickness appears to be the horizontal position. When there is much pain, after the stomach has been well cleared, a few drops of laudanum may be taken, or an opium plaster may be applied over the region of the stomach. Persons about to proceed to sea should put their stomach and bowels in proper order, by the use of mild aperients, and even an emetic, if required, when it will generally be found that a glass of warm and weak brandy-and-water, to which 15 or 20 drops of laudanum, or, still better, 1 or 2 drops of creasote, have been added, will effectually prevent any disposition to sea sickness, provided the bowels be attended to, and excess in eating and drinking be at the same time avoided. A spoonful of crushed ice, in a wine-glassful of cold water, or weak brandy-and-water, will often afford relief when all other means fail. Smoking at sea is very apt to induce sickness. M. F. Curie, in the ‘Comptes Rendus,’ asserts that drawing in the breath as the vessel descends, and exhaling it as it ascends, on the billows, by preventing the movements of the diaphragm acting abnormally on the phrenetic nerves, prevents sea sickness. On this Mr Atkinson, at one of the meetings of the British Association, observed that——if a person, seated on board ship, holding a tumbler filled with water in his hand, makes an effort to prevent the water running over, at the same time allowing not merely his arm, but also his whole body, to participate in the movements, he will find that this has the effect of preventing the giddiness and nausea that the rolling and tossing of the vessel have a tendency to produce in inexperienced voyagers. If the person is suffering from sickness at the commencement of his experiment, as soon as he grasps the glass of liquid in his hand, and suffers his arm to take its course and go through the movements alluded to, he feels as if he were performing them of his own free will, and the nausea abates immediately, and very soon ceases entirely, and does not return so long as he suffers his arm and body to assume the postures into which they seem to be drawn. Should he, however, resist the free course of his hand, he instantly feels a thrill of pain, of a peculiarly stunning kind, shoot through his head, and experiences a sense of dizziness and returning nausea.

Dr Doring, a Viennese physician, states that an ordinary dose of chloral hydrate is an unfailing remedy for sea sickness. In various cases recorded by him it seems to have been of the greatest service, even during long sea voyages, ensuring a good night’s rest, arresting violent sickness when it has set in, and preventing its return.

=SEDATIVE PILLS, Gunther’s.= These are composed of the following ingredients:——Assafœtida powder, 50 parts; extract of valerian, 50; extract of belladonna, 3; oxide of zinc, 1 part; castor, 2 parts. Make into a pill-mass, to be administered in doses of 3 to 10 grains, twice daily, in chorea, &c.

=SED′ATIVES.= _Syn._ SEDATIVA, L. Medicines and agents which diminish the force of the circulation or the animal energy, and allay pain. Foxglove, henbane, tobacco, potassio-tartrate of antimony, and several of the neutral salts and acids, act as sedatives. Cold is, perhaps, the most powerful agent of this class.

=SEED.= _Syn._ SEMEN, L. The seeds of plants are conspicuous for their vast number and variety, and their extreme usefulness to man. The seeds of certain of the _Graminaceæ_ furnish him with his daily bread; some of those of the _Leguminosæ_ in either the immature or ripe state, supply his table with wholesome esculents, or provide a nourishing diet for his domestic animals; whilst those of numerous other plants, dispersed through every class, orders, and family, yield their treasures of oil, medicinals, or perfumes for his use.

=SELEN′IC ACID.= H_{2}SeO_{4}. _Syn._ ACIDUM SELENICUM, L. _Prep._ By fusing selenium with nitrate of potassium or of sodium, acting on the fused mass with water, precipitating the resulting solution with acetate or nitrate of lead, and decomposing the precipitate (selenate of lead), diffused in water, with sulphuretted hydrogen. The selenic acid, thus obtained, may be cautiously concentrated in a glass vessel, if necessary; but if this be pushed too far, it is resolved into selenious acid (H_{2}SeO_{3}) and oxygen.

_Prop., &c._ Hydrated selenic acid is a colourless liquid, closely resembling sulphuric acid; its salts (selenates) bear the closest analogy to the sulphates.

SELENIC ACID (H_{2}SeO_{4}). No selenic anhydride is known. Selenic acid may be obtained in solution by deflagrating selenium or a selenite with potassic nitrate. The residue dissolved in water is mixed with a solution of plumbic nitrate, an insoluble plumbic seleniate being precipitated. The plumbic seleniate is suspended in water and decomposed by means of a current of sulphuretted hydrogen. Plumbic sulphide is precipitated, and the liberated selenic acid separated by filtration is concentrated until it acquires a sp. gr. of 2·6; if heated above 554° F. it decomposes into selenious anhydride, water, and oxygen. Selenic acid has a great resemblance to sulphuric acid. It acts upon the metals in the same manner, and even dissolves gold. The seleniates are also very similar in properties to the sulphates, and both classes of salts are isomorphous. The seleniates give the same characteristic odour before the blowpipe as the selenites. Their solutions give white precipitates with the salts of barium, strontian and lead, insoluble in nitric acid. If a soluble seleniate is boiled with hydrochloric acid, selenic acid is set free, and is reduced to selenious acid, sulphurous acid will then precipitate reduced selenium from the solution. Baric seleniate may be also decomposed in a similar manner, and this reaction distinguishes it from baric sulphate.

=SELE′NIUM.= Se. A rare chemical element, discovered by Berzelius in 1817 in the refuse of a sulphuric acid manufactory near Fahlun, in Sweden, it having been derived from the pyrites employed in the manufacture of the acid. Hence the pyrites of Fahlun forms the chief source of this rare body, although it exists, but less abundantly, in combination with a few other metals, termed selenides. Selenium is chiefly interesting to the chemist from its remarkable analogy in chemical properties to sulphur. Like this latter element, it is capable of assuming three allotropic forms——the amorphous, the vitreous, and the crystalline.

The latter variety of selenium, like the crystalline form of sulphur, dissolves in bisulphide of carbon, but much less readily. Selenium boils below a red heat and becomes converted into a deep yellow vapour, which, when heated, is subject to the same anomalous expansion as sulphur vapour. It is not so combustible as sulphur, which it still further resembles by burning with a blue flame when ignited in the air. During combustion it gives off a peculiar and characteristic smell, resembling that of putrid horse-radish. Heated with strong sulphuric acid, selenium forms a green solution. If this solution is poured into water, the selenium separates and is thrown down. Selenium is without taste or smell, is insoluble in water, and in its normal state is a non-conductor of heat and electricity. Selenium may be extracted from the Fahlun residue by the following process:——It should be first boiled with sulphuric acid, diluted with an equal volume of water, and nitric acid should then be added in small quantities until the oxidation of the selenium is accomplished, which may be known when red fumes cease to be cooled. The solution which contains selenious (SeO_{2}) and selenic (SeO_{3}) acid is then to be largely diluted with water, filtered, the filtrate mixed with about one fourth of its bulk of hydrochloric acid, and then concentrated a little by evaporation, the result of which is that the hydrochloric acid reduces the selenic to selenious acid. A current of sulphurous acid being then passed through the solution, the selenium is precipitated in red flakes, which form into a dense black mass when the liquid is gently heated. The following equation illustrates the reaction:——

H_{2}O,SeO_{2} + H_{2}O + 2SO_{2} = 2(H_{2}SO_{3}) + Se.

Like sulphur, selenium combines with oxygen and forms an anhydride corresponding to sulphurous anhydride. SELENIOUS ANHYDRIDE (SeO_{2}) may be obtained by burning selenium in a current of oxygen; it is, however, more easily prepared by boiling selenium with nitric acid or with aqua regia, the excess of acid being expelled by heat, the selenious anhydride is left as a white mass. When this is dissolved in water it yields a crystalline hydrate of selenious acid (H_{2}SeO_{3}). The salts formed by selenious acid (selenites), with the exception of those of the alkali metals, are mostly insoluble in water. They are easily known by the peculiar odour of selenium which they give off when heated on charcoal in the reducing flame of the blowpipe; solutions of the selenites give a reddish-brown precipitate when treated with sulphurous acid.

=Seleniuretted Hydrogen= (H_{2}Se). This may be obtained in a precisely similar manner, namely, by acting on selenide of iron or potassium with diluted sulphuric or hydrochloric acid. Seleniuretted hydrogen is soluble in water, and precipitates many metals from their salts as selenides. The solution is feebly acid, and, like its analogue solution of sulphuretted hydrogen, if exposed to the air, absorbs oxygen and deposits selenium. The selenides of the alkali metals are soluble in water. The selenides of cerium, zinc, and manganese are flesh-coloured; most of the others are black. This gas is inflammable like sulphuretted hydrogen; it has, however, a still more offensive smell than this latter gas, Berzelius lost his sense of smell for several hours by the application to his nose of a bubble of seleniuretted hydrogen not larger than a pea. There are two chlorides of selenium——a dichloride (Se_{2}Cl_{2}), a volatile liquid of a brown colour, and a tetra-chloride (SeCl_{4}), which occurs as a white crystalline solid. Selenium unites with sulphur, forming a bisulphide (SeS_{2}) and a tersulphide (SeS_{3}). A very curious physical property of selenium when exposed to the action of light was first noticed in 1873 by Mr May, assistant chemist at the Telegraph Station at Valentia, in Ireland, who observed that a stick of crystallised selenium which had been used for some time in telegraphy, where high electrical resistance was required, offered a considerably diminished resistance to the current when exposed to the light than when kept in the dark. Mr May’s discovery, which was at first received with some amount of incredulity, has since been amply corroborated by the observations and researches of many physicists, amongst them by Professor Werner Siemens, the result of whose experiments on this interesting subject we quote from a lecture delivered at the Royal Institution by his brother, Dr William Siemens, in February, 1876. After describing the method by which his brother arranged the selenium, so that, when inserted in the galvanic current of a single Daniell’s cell, the surface action produced by the light upon it attained a maximum effect, and thereby did away with the necessity of employing a large galvanic battery, and at the same time allowed an ordinary galvanometer to be used instead of a delicate one, as hitherto employed, Dr Siemens proceeded to illustrate the action of light upon the element by experiment. “I here hold,” he said, “an element so prepared of amorphous selenium, which I place in a dark box, and insert in a galvanic circuit comprising a Daniell’s cell and a delicate galvanometer, the face of which will be thrown upon the screen through a mirror by means of the electric light.

“In closing the circuit it will be seen that no deflection of the needle ensues. We will now admit light upon the selenium disc and close the circuit, when again no deflection will be observed, showing that the selenium in its present condition is a non-conductor both in the dark and under the influence of light. I will now submit a similar disc of selenium which has been kept in boiling water for an hour and gradually cooled to the same tests as before. In closing the circuit while the plate is in the dark a certain deflection of the galvanometer will be discernible, but I will now open the lid of the box so as to admit light upon the disc, when on again closing the circuit a slight deflection of the galvanometer needle will be observed. In closing the box against the light this deflection will subside, but will again be visible the moment the light is readmitted to the box. Here we have, then, the extraordinary effect of light upon selenium clearly illustrated.

“I will now insert into the same circuit another selenium plate which has been heated up to 210° C, and, after having been kept at that temperature for several hours, has been gradually cooled; it will be observed that this plate is affected to a greater extent than the former by the action of light, and other conditions, to which I shall presently allude, prove the selenium heated to a higher temperature to be in other respects dissimilar to the other two modifications of the same. These differences will be best revealed in describing my brother’s experiment. He placed one of his amorphous preparations of selenium in an air-bath heated above the melting point of selenium (to 260° C.), while the connecting wires were inserted in a galvanic circuit consisting of only one Daniell’s element and a delicate reflecting galvanometer, and every five minutes the temperature and conductivity of the selenium were noted. Up to the temperature of 80° C. no current passed; from this point onward the conductivity of the material rapidly increased until it obtained its maximum at the temperature of 210° C., being nearly its melting point, after which an equally rapid diminution of conductivity commenced, reaching a minimum at a temperature of about 240° C., when the conductivity was only such as could be detected by a most delicate galvanometer. In continuing to increase the temperature of the fluid selenium very gradually but steadily, its conductivity increased again.

The interpretation of these experiments is as follows: Amorphous selenium retains a very large amount of specific heat, which renders it a non-conductor of electricity: when heated to 80° this amorphous solid mass begins to change its amorphous condition for the crystalline form, in which form it possesses a greatly reduced amount of specific heat, giving rise to the increase of temperature beyond that of surrounding objects when the change of condition is once set in. If care is taken to limit the rise of temperature of the selenium to 100° C., and if it is very gradually cooled after being maintained for an hour or two at that temperature, a mass is obtained which conducts electricity to some extent, and which shows increased conductivity under the influence of light. But in examining the conductivity of selenium so prepared at various temperatures below 80°, and without accession of light, it was found that its _conductivity increases with rise of temperature_, in which respect it resembles carbon, sulphide of metals, and generally electrolytes. This my brother terms his first modification of selenium.

But in extending the heating influence up to 210°, and in maintaining that temperature by means of a bath of paraffin for some hours before gradually reducing the same, he obtained a second modification of selenium, in which its conductivity increases with fall of temperature, and in which modification it is, therefore, analogous to the metals. This second modification of selenium is a better conductor of electricity than the first, and its sensitiveness to light is so great that its conductivity in sunlight is fifteen times greater than it is in the dark, as will be seen from the following table, in which is given the effects of different intensities of light on selenium (Modification II) obtained at Woolwich on the 14th of February, 1876:——

---------------------------------------------------------------
Selenium in |Relative Conductivities. | Resistance in
|-------------------------| Ohms.
|Deflections. | Ratio. |
| | |
---------------------------------------------------------------
1. Dark | 32 | 1·0 | 10,070,000
2. Diffused | | |
daylight. | 110 | 3·4 | 2,930,000
3. Lamplight | 180 | 5·6 | 1,790,000
4. Sunlight | 470 | 14·7 | 680,000
---------------------------------------------------------------

Unfortunately, however, the second modification is not so stable as the first; when lowered in temperature parts of it change back into the first or metalloid modification by taking up specific heat, and in watching this effect a point is discovered at which ratio of increase of conductivity with fall of temperature changes sign, or where the electrolyte substance appears to predominate over the metallic selenium. If cooled down to 15° C., the whole of the metallic selenium is gradually being converted back into the first variety. The physical conclusions here arrived at may be said to be an extension of Helmholtz’s theory that the conductivity of metals varies inversely as the total heat contained in them. Helmholtz had only the sensible heat of temperature (counting from the absolute zero point) in view, but it has already been shown by Hittorf and Werner Siemens that it applies in the case of tin and some other metals, also to specific heat and to the latent heat of fusion. In selenium the specific heat is an extremely variable quantity, changing in the solid mass at certain temperatures, and, it is contended, under the influence of light. Aided by these experimental researches, my brother arrives at the conclusion that the influence of light upon selenium may be explained by a “_change of its molecular condition near the surface, from the first or electrolyte into the second or metallic modification_, or in other words, by a _liberation of specific heat upon the illuminated surface of crystalline selenium_, which liberated heat is reabsorbed when the liberating cause has ceased to act.” Professor Adams, who has likewise investigated this singular action of light upon selenium, ascribes it to a different cause. He says:——

1. That the light falling on the selenium causes an electromotive force in it in the same direction as the battery current passing through it, the effect being similar to the effect due to polarisation in an electrolyte, but in the opposite direction.

2. That the light falling on the selenium causes a change on its surface akin to the change which it produces on the surface of a phosphorescent body, and that in consequence of this change the electro-current is enabled to pass more readily over the surface of the selenium.

=SEM′OLA (Bullock’s).= This preparation consists of wheaten flour deprived of much of its starch by washings with water, and contains the largest amount (48 per cent.) of nitrogenous or albumenoid principles consistent with its adaptability to culinary purposes. It is specially intended as a food for infants, weakly children, and invalids.

=SEMOLI′NA.= _Syn._ SÉMOULE, SEMOULINA. The large hard grains of wheat flour retained in the bolting machine, after the fine flour has passed through its meshes. “The best sémoule is obtained from the wheat of the southern parts of Europe. With the sémoule the fine white Parisian bread called ‘_gruau_’ is baked.” (Ure.)

=SEN′EGA.= _Syn._ SENEKA, SNAKEROOT, RATTLESNAKE R.; SENEGÆ RADIX (B. P.); SENEGA (Ph. L., E., & D.), RADIX SENEGÆ, L. “The root of the _Polygala Senega_, Linn.” (Ph. L.) A stimulating diaphoretic, and expectorant; in large doses diuretic, cathartic, and emetic. In America it is used as an antidote to the bite of the rattlesnake. Drs Chapman and Hartshorne extol it as an emmenagogue. Dr Pereira says that it is an exceedingly valuable remedy in the latter stages of bronchial or pulmonary inflammation, when this disease occurs in aged, debilitated, or torpid constitutions.——_Dose_, 10 to 30 gr., in powder or decoction (combined with aromatics, opium, or camphor), thrice daily.

According to Patrouillard senega is occasionally adulterated with the roots of _Asclepias vincetoxicum_. The branches of the latter root are cylindrical, very white, and almost devoid of taste; those of senega, on the contrary, are yellowish and twisted, and have a very acrid taste. The froth produced by shaking an infusion of senega keeps much longer than that produced by an infusion of the adulterant. In other respects there is a great resemblance between the two roots.

=SEN′EGIN.= _Syn._ POLYGALIN, POLYGALIC ACID. A white odourless powder, discovered by Gehlin in the bark of seneka root (_Polygala Senega_).

=SEN′NA.= _Syn._ SENNA, SENNÆ FOLIA, L. There are three principal varieties:——

1. ALEXANDRIAN SENNA (SENNA ALEXANDRINA——B. P., Ph. L., E., & D.), referred in the, Ph. L. to _Cassia officinalis_ and _Cassia obovata_, in the Ph. D. to _Cassia acutifolia_ (Delile), and in the Ph. E. to various species of cassia. The leaves are “unequal at the base, ovate acute, or obovate mucronate.” (Ph. L.) It is generally mixed with the leaves of _Solenostemma Argel_ (argel leaves), the presence of which is often the occasion of much griping. The leaf of argel is fully an inch long, warty, regular in its formation, and the lateral nerves are imperfectly seen on the under side; whilst that of the true Alexandrian senna never exceeds 3/4 inch in length, is oblique, and the nerves on the under side are very conspicuous.

2. INDIAN SENNA (SENNA INDICA——B. P.; Ph. L., & E.) is referred to _Cassia officinalis_ in the Ph. L., and in the Ph. E. & D. to _Cassia elongata_ (Lemaire, Lisancourt). The leaf is “unequal at the base,” and “Lanceolate.” (Ph. L.)

3. TINNEVELLY SENNA, forming the finest Indian, now introduced into the Ph. D., is therein described as composed of the leaflets of _Cassia oblongata_. These are pale green, thin, flexible, and from 1 to 2 inches long, and nearly 1/2 inch broad. This variety is equal in medicinal virtue to the best Alexandrian, and is to be preferred, on account of its being imported perfectly free from adulteration.

Senna is purgative in doses of 10 to 30 gr., either in powder or made into an infusion of tea with Water, combined with ginger, caraways, or some other aromatic, to prevent griping. It acts chiefly on the small intestines, and generally effects its purpose within 4 hours after being taken.

=SE′′PIA.= A pigment prepared from the ‘ink’ or black fluid secreted by _Sepia officinalis_ (Linn.), and several other varieties of cuttle-fish. The contents of the ‘ink bags’ are inspissated as soon as possible after collection, and then form the crude sepia of commerce. This is prepared for artists by boiling it for a short time in a weak lye of caustic alkali, precipitating the solution with an acid, and well washing and carefully drying the precipitate by a gentle heat. It possesses a fine brown colour, and is used like Indian ink.

=SER′PENTARY.= _Syn._ VIRGINIAN SNAKE-ROOT; SERPENTARIA RADIX (B. P.), SERPENTARIÆ RADIX, SERPENTARIA (Ph. L. & E.), ARISTOLOCHIA SERPENTARIA (Ph. D.), L. An excellent stimulating diaphoretic and tonic; in typhoid and putrid fevers, dyspepsia, &c. It is admirably suited to check vomiting and to tranquilise the stomach, particularly in bilious cases. (Dr Chapman.)——_Dose_, 10 to 20 gr., every third or fourth hour, its use being preceded by an aperient.

=SE′′RUM.= _Syn._ SERALBUMEN. The clear pale fluid in which the blood-globules float, and which separates from blood during its coagulation. It is, essentially, a feebly alkaline solution of albumen. See ALBUMEN.

=SESQUI-.= See NOMENCLATURE.

=SE′TON.= _Syn._ SETACEUM. An artificial ulcer, made by passing a portion of silk or thread under the skin by means of a seton needle, a part of which is drawn through daily, and thus keeps up a constant irritation. Occasionally the thread is anointed with some irritating substance for the purpose of increasing the discharge.

=SEVEN SEALS, or Golden Wonder——Dr Radcliffe’s Great Remedy.= According to the prospectus, this remedy is good for cholera morbus, dysentery, diarrhœa, burns, sprains, rheumatism, warts and corns, and all diseases. In a quadrangular bottle we find about 95 grammes of a brownish-orange clear fluid, which is a spirituous tincture of cayenne pepper mixed with ether, chloroform, American oil of peppermint, and a little camphor. The proportion of these ingredients is, approximately, 4 grammes ether, 6 grammes chloroform, 4 gramme camphor or camphoraceous oil, 2 grammes oil of peppermint, 35 grammes tincture of capsicum. 50 grammes spirit of wine (90 per cent.) (Hager.)

=SE′VUM (Prepared).= _Syn._ SEVUM PRÆPARATUM (B. P.), SEVUM MAGNETICUM, L. _Prep._ 1. (‘Pharm. Journ.’) Mould candles, at least 2 years old, melted by a very gentle heat, and strained from the wicks.

2. As MAGNETIC ADEPS. Used to make mercurial ointment. Triturated with 8, 12, or 16 times its weight of quicksilver, the globules are completely extinguished in from 10 to 15 minutes.

=SEWAGE, Removal and Disposal of.= The waste and putrescible refuse discharged from dwelling-houses by house-pipes and drains into sewers may be said, in general terms, to consist, besides human fæces and urine,[150] of the dirty water and soapsuds arising from washing our bodies, our houses, and linen, more or less foul, as well as the water which, having been used for cooking operations, necessarily contains variable quantities of mineral and vegetable matter.

[Footnote 150: In the drainage of some towns the fæces are not allowed to enter the sewers. This, however, is the exception.]

The above statement will have prepared us not only for the complex nature of sewage water as shown in the following tables, but also for the variability in the amount of its constituents, this latter condition depending upon locality, and, as experiment shows, the hour of the day at which the sewage was collected.

_Composition of Sewer Water_ (WAY).

+-------------------------------+----------------------------------+
| | Grains per Gallon. |
| +--------+-------+-------+---------+
| | 1. | 2. | 3. | 4. |
+-------------------------------+--------+-------+-------+---------+
|Organic matters (soluble) | 19·40 | 41·03 | 12·30 | } 9·20 |
|Organic matters (suspended) | 39·10 | 17·00 | 24·37 | } |
|Lime | 10·13 | 14·71 | 12·52 | 11·25 |
|Magnesia | 1·42 | 1·82 | 1·59 | 1·35 |
|Soda | 4·01 | 2·40 | 2·41 | 1·89 |
|Potash | 3·66 | 3·57 | 3·31 | 1·09 |
|Chloride of Sodium | 26·40 | 22·61 | 34·30 | 5·58 |
|Sulphuric Acid | 5·34 | 5·31 | 6·40 | 3·43 |
|Phosphoric Acid | 2·63 | 5·76 | 2·48 | 0·64 |
|Carbonic Acid | 9·01 | 8·92 | 11·76 | } |
|Silicia {Oxide of Iron} | 6·20 | 13·55 | 6·46 | } 4·77 |
| {Oxide of Zinc} | | | | |
|Ammonia | 7·48 | 8·43 | 7·88 | |
| +--------+-------+-------+---------+
| |134·78 |145·11 |125·78 | 39·20 |
+-------------------------------+--------+-------+-------+---------+

_London Sewer Water_ (LETHEBY).

+-----------------+---------------------------------------------+
| | Grains per gallon. |
| +--------------+--------------+---------------+
| | Day Sewage. | Night Sewage.| Storm Sewage. |
+-----------------+--------------+--------------+---------------+
|Soluble matters | 55·74 | 65·09 | 70·26 |
|Organic matters | 15·08 | 7·42 | 14·75 |
|Nitrogen | 5·44 | 5·19 | 7·26 |
|Mineral matters | 40·66 | 57·67 | 55·71 |
|Phosphoric acid | 0·85 | 0·69 | 1·03 |
|Potash | 1·21 | 1·15 | 1·61 |
|Suspended matters| 38·15 | 13·99 | 31·88 |
|Organic | 16·11 | 7·48 | 17·55 |
|Nitrogen | 0·78 | 0·29 | 0·67 |
|Mineral | 22·04 | 6·51 | 14·33 |
|Phosphoric acid | 0·89 | 0·64 | 0·98 |
|Potash | 8·08 | 0·04 | 0·16 |
+-----------------+--------------+--------------+---------------+

Letheby states that the sewer water in towns with water-closets has the following average composition per gallon:

Organic matter 27·72
Nitrogen 6·21
Phosphoric acid 1·57
Potash 2·03

Sewer water placed under the microscope reveals various dead decaying matters, besides swarms of bacteria, ciliated infusoria, amœbiform bodies, and fungi, consisting of spores and mycelium. The rotifera, diatoms, and desmids are few in number.[151] That a fluid having a composition such as sewage water has been shown to possess, when mixed with solid excreta, would, from the decomposition that so soon takes place in it, seriously endanger the health of those in whose habitations it was allowed to remain, is so self-evident to the sanitarian and pathologist that it is no wonder every civilised community should endeavour to get rid of this refuse from their habitations as speedily and effectively as possible. But the removal of the home sewage is a proceeding as illogical as it is imperfect if we afterwards neglect so to dispose of it as to render it innocuous or devoid of danger to the public health. The old method of getting rid of sewage (even when deprived of the fæcal matter) by turning it into rivers and streams, has, more particularly since the Report of the Rivers Pollution Commissioners in 1870, been gradually abandoned. That when sewer water passes into a river it undergoes a great amount of purification from oxidation, subsidence, and the agency of water-plants is undeniable.

[Footnote 151: Parkes.]

Letheby considered that if sewage mixed with twenty times its bulk of water flowed for nine miles it would be perfectly oxidised. It appears, however, from the experiments of Frankland, that so far as sewage when mixed with twenty times its volume of water being oxidised during a flow of ten or twelve miles, scarcely two thirds of it would be so destroyed in the flow of 168 miles, at the rate of one mile per hour, or after the lapse of a week. The results of Frankland’s experiments led him to infer that there is no river in the United Kingdom of sufficient length to effect the destruction of sewage by oxidation; and he adds, “there is no process practicable on a large scale by which the noxious material (sewage matter) can be removed from water once so contaminated, and, therefore, I am of opinion that water which has been once contaminated by sewage or manure matter is thenceforth unsuitable for domestic use.”

The discharge of sewage water, whether with or without solid excreta, into our springs and rivers, was a practice so dangerous and prejudicial to health that it is no cause for wonder the Legislature should, during the session of 1876, have passed a measure the object of which was after the lapse of one year to facilitate legal proceedings being instituted against persons who permitted sewage or other deleterious refuse to flow into rivers or streams. This measure, known as the “Rivers Pollution Prevention Act,” is now in force, and permits offenders to be proceeded against; but it still leaves unsolved the important hygienic problem——How are we ultimately and with safety to the community to dispose of our sewage?

The numerous processes (the chief of which will be brought under notice) proposed for the attainment of this end have been divided by writers and authorities on sanitary science into——

1. WET METHODS.

2. DRY METHODS.

1. WET METHODS. These comprise the removal of excreta——(1) By discharging it into running water. (2) By storage in tank with overflow. (3) By carrying it into the sea. (4) By precipitation. (5) By irrigation and filtration.

(1) _By discharging it into running water._ Our previous remarks have already shown in what respect this proposal is fallacious, and why it has, therefore, been discontinued.

(2) _By storage in tank with overflow._ In this process the sewage runs into a well-cemented tank fitted with an overflow pipe, which sometimes leads into a second tank arranged in the same manner; the solids subside, and are removed from time to time, whilst the liquid is allowed to run away. Instead of permitting the liquid to escape into a ditch or stream, it has been proposed to carry it into drain pipes, which are buried from half a foot to a foot in the subsoil, where it will be readily sucked up by the roots of grasses. This plan is only suited for small villages, or for a single house or mansion.

(3) _By carrying it into the sea._ The precautions to be observed in the working of this system are, wherever possible, to let the outlet or discharge pipe, which conveys the sewage to the sea, be always under water even at ebb tide, and to take special care that the wind does not blow up the sewers. A tide-flap, opening outwards, which is usually fixed by a hinge on the sewer at its outlet, will obviate this last contingency. At high water the tide will fill the outfall sewers to its own level, and to that extent will check the discharge of sewage, and thus cause a deposit in the sewers filled with mixed sea water and sewage. It is most important that this should be removed.

“If the sewage cannot be got well out to sea, and if it issues in narrow channels, it may cause a nuisance, and may require to be purified before discharge.”[152]

[Footnote 152: Parkes.]

(4) _By precipitation._ The simplest of the plans proposed for this method of removal is by subsidence only, and would afterwards permit the discharge of the supernatant sewage water into running water or over the land. The removal of the solid material is effected in a manner somewhat similar to that followed in plan No. 2, but as the thin water which runs off must, when poured into rivers or streams, be almost as dangerous as the sewage itself, the process of precipitation by settlement alone has little to commend it over the old rude and objectionable practice, a circumstance that in these days will doubtless lead to its entire prohibition.

In order to ensure greater purification the sewage in the subsiding tanks is now usually mixed with certain chemical reagents, which, it is believed, have the effect not only of speedily precipitating the solid materials, but also carrying down injurious matters suspended in the sewage water, thus rendering it sufficiently pure to be discharged without risk to health into any watercourse.

Of the numerous precipitants employed for this purpose, we may mention the following:

_Lime and salts of lime._ Quicklime, in the proportion of 8 gr. to a gallon of water; or 1 lb. to about 600 galls. of sewage; lime, with the addition of about a fortieth of its weight of chloride of lime; calcic phosphate dissolved in sulphuric acid; Whitehead’s patent, which consists of a mixture of mono- and dicalcic phosphate; chloride of calcium.

_Aluminous compounds._ Bird’s process——A mixture of aluminous earths and sulphuric acid. Andersons and Lenk’s——Impure sulphate of alum; refuse of alum works, either alone or mixed with lime or charcoal. Scott’s cement process——Clay mixed with lime; natural phosphate of aluminium dissolved by sulphuric acid and mixed with lime.

The quantities of the above substances when used as precipitants vary, in some of them fifty, and in others eighty grains to a gallon of sewer water being employed.

_Magnesium salts._ Impure chloride of magnesium mixed with superphosphate of lime.

_Carbon._ As vegetable charcoal, peat, seaweed charcoal, carbonised tan, lignite, and Boghead coke.

_Iron._ In the form of sulphate. Ellerman’s and Dale’s——Perchloride; the sulphate is sometimes mixed with coal dust.

_Manganese._ Condy’s fluid.

_Zinc._ As sulphate and chloride.

_Sillar’s process._ The A. B. C. process, so called because composed of alum, blood, charcoal, and clay.

_Hill’s process._ Lime and tar are the precipitants. The effluent water is filtered through charcoal. The question now arises as to whether the sewer water after treatment with any of the above substances is in a fit condition to be poured into a stream or river. The Rivers Pollution Commissioners in their first and second reports give a number of analyses, from which it appears that on an average the chemical treatment removes 89·8 per cent. of the matters suspended in the sewage waters, but only 36·6 per cent. of the organic nitrogen is dissolved in them.

Of the A. B. C. process, Mr Crookes states that, when properly carried out, it removes all the phosphoric acid; and Professor Voelcker’s analysis of the effluent water from sewage treated by the acid phosphate of alumina process gives more ammonia than the original sewer water, less organic nitrogen by one half, and less phosphoric acid. Such a water is said by some authorities to be pure enough to be discharged into streams.

_General Scott’s process._ General Scott proposes to treat the sewer water with lime and clay, and instead of employing the precipitate obtained by this means as a manure, would, after burning it, use it as cement. He argues that the deposit contains so much combustible matter as to considerably reduce the quantity of coal usually expended in the manufacture of cement, and consequently the cement could be sold at a remunerative price.

This, like the ‘carbonisation’ process, possesses the merit of effectually destroying any noxious principles present in the deposit.

Commenting on the various precipitation processes Dr Parkes writes:——“When the sewer water is cleared by any of these plans is it fit to be discharged into streams? In the opinion of some authorities, if the precipitate is a good one it may be so, and it appears certain that in many cases it is chemically a tolerably pure water, and it will no longer silt up the bed nor cause a nuisance. But it still contains, in all cases, some organic matter, as well as ammonia, potash, and phosphoric acid. It has, therefore, fertilising powers certainly, and possibly it has also injurious powers. No proof of this has been given, but also no disproof at present, and when we consider how small the agencies of the specific diseases probably are, and how likely it is that they remain suspended, we do not seem to be in a position to expect that the water, after subsidence of the deposit, will be safe to drink.

(5) _By irrigation and filtration._ By this process is meant the passing of the sewer water over and through soil, with the object not only of effecting its purification to such an extent as to render it fit to be discharged into a river or stream, but also of employing it as a valuable manure. In the present article we shall treat only of the application of the process to the first of these purposes.

There is ample evidence to show that, if carried out with due attention to detail, no process for the treatment of effluent sewage water, so as to render it innocuous, is equal to that which subjects it to irrigation and filtration.

The Rivers Pollution Commissioners thus report on it:——“We are, therefore, justified in recommending irrigation as a safe as well as profitable and efficient method of cleansing town sewage.”

The conditions necessary for the successful carrying out of this system are thus stated by Mr T. J. Dyke, in explaining “the process of the downward intermittent filtration of sewage at Troedyrhiw, near Merthyr Tydvil:”——“1. The soil of the land to be used must be porous. 2. A main effluent drain, which must not be less than six feet from the surface, must be provided. 3. The surface of the soil to be so inclined as to permit the sewage stream to flow over the whole land. 4. The filtering area should be divided into four equal parts, each part to be irrigated with the sewage for six hours, and then an interval of eighteen hours to elapse before a second irrigation takes place; each of the four parts would thus be used for six hours out of the twenty-four. An acre of land so prepared would purify 100,000 gallons of sewage per day.” At Troedyrhiw the sewage has lime added to it, and the mixture is strained through cinders into tanks. From the tank it flows on to the conduit, by which it is conveyed to the filtering areas.

“These consist of about twenty acres of land, immediately adjoining the road on which the tanks are placed, and have been arranged into filtering areas or beds on a plan devised by Mr J. Bayley Denton. The land is a loamy soil, eighteen inches thick, overlying a bed of gravel. The whole of these twenty acres have been underdrained to a depth of from five to seven feet. The lateral drains are placed at regular distances from each other, and run towards the main or effluent drain. This is everywhere six feet deep. The surface of the land is formed into beds; these have been made to slope towards the main drain by a fall of 1 in 150.

“The surface is ploughed in ridges; on these vegetables are planted or seeds sown. The line of the ridged furrow is in the direction of the under drain. Along the raised margin of each bed, in each area, delivering carriers are placed, one edge being slightly depressed.

“The strained sewage passes from the conduits into the delivery carriers, and as it overflows the depressed edges runs gently into and along the farrows down to the lowest and most distant part of the plot. The sewage continues to be so delivered for six hours, then an interval of rest of eighteen hours takes place, and again the land is thoroughly charged with the fertilising stream. The water percolates through the six feet of earth, and reaches the lateral drains, which convey it to the main effluent drain.

“The result of this plan of disposing of sewage by downward intermittent filtration, may be seen in samples of the effluent water taken from the outlet of the main drain. Such water is bright, perfectly pellucid, free from smell, and tastes only of common salt. It may be safely drunk——in fact, is used by the workmen employed on the farm. During the process of irrigation no nuisance is caused, for the soil quickly absorbs all the fluids passed on to it; in fact, in two or three hours after the water has ceased to flow on the land, an observer would say that the ground had not been wetted for days. The workmen say that no unpleasant smell is noticed, nor has the health of the persons employed, in any one instance, been affected by any presumed poisonous exhalation.

“The only imperfection of the plan is that, at the end of the furrows nearest the lowest corner of a plot, a slight deposit of scum is formed. This scum is formed by the fine insoluble precipitate caused mainly by the addition of lime to the sewage stream.”

The table below, taken from the report of the Rivers Pollution Commissioners, gives the composition of the effluent water after it has passed through the soil.