Chapter LXI: Part 2 (22)

If those results be compared with the condition of the supernatant sewage water, after treatment by any of the chemical precipitants already enumerated, the inferiority of these latter as methods of removal of the organic impurity of the sewage water will be evident.

The best of these precipitants give a removal of only 65·8 per cent. of organic nitrogen, whilst the A. B. C. process shows a diminution of 58·9 only. It appears from the first and second reports of the Rivers Pollution Commissioners, that on an average the precipitation processes remove 89·8 per cent. of the suspended matters, but only 36·6 per cent. of the organic nitrogen dissolved in the liquid.

The effects of a soil upon sewage water passing through it are the following:——

1. The filtering property of the soil mechanically arrests and retains the suspended particles of the sewage.

2 and 3. The porosity and physical attraction of the soil lead to the oxidation of the organic matter contained in the sewage, as instanced in the discovery of nitrates and nitrites in the effluent water, which did not exist previous to filtration.

4. A chemical reaction takes place between the constituents of the sewage and those of the soil.

If the charges brought against the system of irrigation, viz. that it is detrimental to the health and comfort of those who reside near sewage farms cannot be denied, it seems pretty certain that, in most cases, any ill effects arising from the method may be traced to its defective management. The selection of the soil which is to receive the sewage is a highly important consideration. The best for this purpose seems to be a loose marl, containing oxide of iron and alumina; but sand, as well as chalk, are both said to answer excellently.

+-------------------------------------------+-----------------------+----------+
| |Percentage of dissolved|Percentage|
| |Organic Pollution |suspended |
| | removed. |Organic |
|Results of irrigation, in part per 100,000.+----------+------------+Pollution |
| | Organic | Organic |removed |
| | Carbon. | Nitrogen. | |
+-------------------------------------------+----------+------------+----------+
| | | | |
|On fallow land at Chorley (adhesive loam) | 62·3 | 70·2 | 100· |
|At Edinburgh (both sand and clay) | 45·3 | 81·1 | 84·9 |
|Barking (gravelly soil) | 65·8 | 86·2 | 100· |
|Aldershot (light sand)—— | | | |
| Best result | 91·8 | 87·3 | 99·7 |
| Worst result | 69·9 | 82·9 | 87·7 |
| Average result | 80·9 | 85·1 | 93·7 |
|Carlisle (light loam) | 77·9 | 59·8 | 100· |
|Penrith (light loam) | 75·0 | 77·2 | 100· |
|Rugby (adhesive soil) | 72·3 | 92·9 | 96·0 |
|Banbury (principally clay)—— | | | |
| Best result | 87·8 | 91·3 | 96·0 |
| Worst result | 64·1 | 80·1 | 90·3 |
| Average result | 76· | 85·7 | 93·2 |
|Warwick (stiff clay) | 71·7 | 89·6 | 100· |
|Worthing (loam) | 42·7 | 85·3 | 100· |
|Bedford (light gravelly soil), | | | |
| average result | 71·6 | 81·3 | 100· |
|Norwood (clay), average result | 65·0 | 75·1 | 100· |
|Croydon (gravelly soil)—— | | | |
| Best result | 73·2 | 93·2 | 100· |
| Worst result | 61·6 | 90·4 | 100· |
| Average result | 67·4 | 91·8 | 100· |
+-------------------------------------------+----------+------------+----------+

If the soil be of a stiff clayey nature it must be broken up and mixed with sand, lime, or ashes. The upper parts must be comminuted and rendered porous, and it must be efficiently and deeply drained. At Troedyrhiw, as we have seen, the effluent drain is six feet deep.

The sewer water should be poured over the land in as fresh a condition as possible, having been previously deprived of any solid or grosser parts by straining. At Carlisle, decomposition of the sewage during its flow is prevented by adding carbolic acid to it. Lastly, it is of the utmost consequence that the amount of land used as the filtering medium shall be large. Letheby has shown that where this precaution is neglected, not only is the purification of the sewage incomplete, but the plan becomes a public nuisance. The amount of filtering earth should not be less than one cubic yard for eight gallons of sewage in twenty-four hours, in properly prepared soils; in some soils more than a cubic yard is required.

The late Dr Parkes has given a summary of various reports that have from time to time been issued as to the effects of sewage farms upon the public health and comfort. He says:——“That sewage farms, if too near to houses, and if not carefully conducted, may give off disagreeable effluvia is certain; but it is also clear that in some farms this is very trifling, and that when the sewer water gets on the land it soon ceases. It is denied by some persons that more nuisance is excited than by any other mode of using manure. As regards health, it has been alleged that these farms may——1st, give off effluvia which may produce enteric fever or dysentery, or some allied affection; or, 2nd, and in the spread of entozoic diseases; or, 3rd, make ground swampy and marshy, and may also poison wells, and thus affect health.”

The evidence of Edinburgh, Croydon, Aldershot, Rugby, Worthing, Romford, the Sussex Lunatic Asylum, is very strong against any influence in the production of typhoid by sewage farms effluvia. On the other hand, Dr Clouston’s record of the outbreak of dysentery in the Cumberland Asylum is counter evidence of weight, and so is one of the cases noted by Letheby of typhoid fever outbreak in Copley, when a meadow was irrigated with the brook water containing the sewage of Halifax.

The negative evidence is, however, so strong as to justify the view that the effluvia from a well-managed sewage farm do not produce typhoid fever, or dysentery, or any affection of the kind. In a case at Eton in which some cases of enteric fever were attributed to the effluvia, Dr Buchanan discovered that the sewer water had been drunk; this was more likely to have been the cause.

With regard to the second point, the spread of entozoic diseases by the carriage of the sewer water to the land, has been thought probable by Cobbold, though as solid excreta from towns have been for some years largely employed as manure, it is doubtful whether the liquid plans would be more dangerous. The special entozoic diseases which, it is feared, might thus arise, are tapeworms, round worms, trichina, Bilharzia, and distoma hepaticum in sheep. Cobbold’s latest observations show that the embryos of Bilharzia die so rapidly, that even were it introduced into England there would be little danger.

The trichina disease is only known at present to be produced in men by the worms in the flesh of pigs which is eaten, and it seems doubtful whether pigs receive them from the land. There remain, then, only tapeworms and round worms for men and distoma hepaticum for sheep to be dreaded. With regard to these, the evidence at present is negative; and though much weight must be attached to any opinion of Cobbold’s, this argument against sewage irrigation must be admitted to want evidence from experience.

The third criticism appears to be true.

The land may become swampy and the adjacent wells poisoned, and disease (ague, and perhaps diarrhœa and dysentery) be thus produced. But this is owing to mismanagement, and when a sewage farm is properly arranged it is not damp, and the wells do not suffer.[153]

[Footnote 153: ‘Practical Hygiene.’]

The foregoing processes for the removal of excreta from dwellings necessitates the joint employment of sewers and large quantities of water. It may, however, sometimes happen that the adoption of either of these appliances may be not only difficult, but altogether impracticable; as for instance, in localities where a sufficient fall cannot be obtained for the sewers; or where the supply of water is not adequate; or when the severity of the climate at certain times is such, that for months in the year the water is frozen. Under these conditions the excreta must either be allowed to accumulate about houses, or else be removed by methods other than those we have described, at more or less short intervals. Of course their speedy removal is the best and safest; but in cases where they are permitted to accumulate, it is essential they should be mixed with deodorants, and confined in properly constructed receptacles (as far as possible from dwellings), from which category such pre-eminently unsanitary arrangements as cesspools and dead wells must be excluded.

When excreta are got rid of from houses by other means than those of sewers and water, the processes employed are termed,

2. DRY METHODS. These comprise——

1. Removal of the excreta without admixture.

2. Removal of the excreta after treatment with deodorising and anti-putrescent substances.

1. _Removal without admixture._ In some cases boxes and tanks receive the ordure and urine, and these are changed more or less frequently.

In Glasgow the excreta from a part of the city containing eighty thousand people is thus collected and removed without admixture,[154] daily.

[Footnote 154: Except that from the garbage of the houses.]

In Edinburgh there are also many closets supplied with movable metal pails, which are likewise removed daily. Many large dwelling-houses in this latter city are entirely without water-closet accommodation; hence the custom of placing pails full of excrement, urine, &c., outside the houses to be taken away by the scavenger. In Rochdale the excrement, &c., is collected in tubs, with tight-fitting lids, which are emptied twice or thrice a week. These tubs are manufactured out of disused paraffin casks. In Leeds, also, the excreta are collected in boxes without being subjected to admixture. In some towns in the north of England the excreta fall into receptacles constructed upon what is termed the ‘Goux’ principle. In this system the pails or receptacles are lined with some absorbent lining, which abstracts the urine;[155] another contrivance is to have the receptacle fitted with a pipe or drain; the object in each case being to render the fæces drier and to delay their decomposition.

[Footnote 155: The refuse of cloth manufacturers is chiefly used for this purpose.]

The pail or tub system (Fosses Mobiles) which is employed in Belgium, has for its object the collection of the fæces in a state of purity, without admixture with water, in a clean and odourless condition.

The apparatus for carrying it out consists of——

1. _The seat._ This consists simply of a soil-pan of stoneware or _faïence_, without woodwork, the soil-pan merely projecting from the top of the descent pipe. Its borders are furnished with a groove filled with water or sand, into which the raised rim of the lid fits.

2. _The connecting pipe._ This pipe is straight without a syphon, and joins the descent pipe at the very acute angle of 22°, and is about 4 inches in diameter inside. It is, like the next, made of stoneware, glazed inside.

3. _Descent pipe._ This is from 6 to 8 inches in internal diameter; it is vertical, and is composed of a series of pipes, connected with each other by dry sand joints, without cements, fixed to the wall by iron bands.

It rests at the ground-floor level on a strong flagstone. Its prolongation through and below this stone consists of a sliding pipe of wrought copper capable of being lengthened or shortened, and solidly fixed to the stone by a cast-iron connector. A sort of circular shallow dish (_ecuelle_), which can be hung under this last part of the descent pipe, serves at a given moment to shut its lower orifice.

4. _Tub_ (Tonneau). The excremental matters coming down the descent pipe fall into a tub of from 2 to 3 hectolitres (44 to 66 gallons), in a hole in the top of which the lower part of the pipe fits tightly. A cover fitted with a spring serves to shut and lute the tub when it is full. Placed on a stand furnished with wheels, the tub is easily managed.

When filled it is immediately replaced by another similar contrivance. If the tub is underground, the rails (on which the stand moves) should be placed on an incline, so that the removal and replacement may be easily effected. The underground chamber must be isolated, and the entrance to it placed outside the building. The thorough tarring of the interior of the tub not only preserves the staves, but also partly neutralises the effect of the mephitic gases which the excremental matters discharge.

_Ventilation pipe._ To prevent the smells and gases which are given off from the mouth of the tub from spreading themselves (in the house) by means of the opening in the privy seat, at the upper extremity of the descent pipe, is fixed a ventilation pipe, which rises above the coping of the roof, and the action of which is increased by means of a vane, or any other contrivance producing the same effect.[156]

[Footnote 156: Corfield.]

It is said that in the working of any of the above processes, little or no nuisance ensues, if only ordinary care and intelligence are used. In many cases the excreta collected by the methods above specified is conveyed to manufactories and then converted into manure.

It does not appear that in England the health of the workmen employed in a manure manufactory or of those who live in the neighbourhood of it suffers in consequence.

_Removal of the excreta after treatment with deodorising and antiputrescent substances._ This is the method usually adopted when the dry process is followed; the excreta mixed with the deodorising substance when removed from the house being at once applied to the land.

_a._ _Coal and wood ashes._ It is a common practice in the north of England to throw coal ashes on the excreta, which fall into closets made with hinged flaps or seats for the purpose of admitting the ashes, as at Manchester and Salford. Wood ashes are far more effective deodorisers than coal ashes, but they are seldom procurable. “In some towns there are receptacles called ‘middens,’ intended both for excreta and ashes; sometimes these are cemented, and there may be a pipe leading into a sewer so as to dry them. The midden system is a bad one; even with every care, the vast heaps of putrefying material which accumulate in some of our towns must have a very serious influence on the health, and the sooner the middens are abolished the better.”[157]

[Footnote 157: Parkes.]

_b._ _Deodorising powders._ At some of the Indian stations deodorants, such as M’Dougall’s, or Calvert’s carbolic acid powders, have been successfully employed, a comparatively small quantity being mixed with the excreta.

In Germany a mixture of lime, chloride of magnesium, and tar is largely used for the same purpose, and is known as Süverns’ deodoriser.”

Another deodoriser (the Müller Schür), also used in the dry method, is composed of lime, 100 lbs.; powdered wood charcoal 20 lbs.; peat powder or sawdust, 10 lbs.; and carbolic acid (containing 60 to 70 per cent. of real acid) 1 lb. After having been mixed, the mass is placed under cover for a night to avoid any chance of spontaneous ignition, and when dry it is packed in barrels.

_c._ _Charcoal._ The powerfully deodorising properties of charcoal obviously adapt it for the removal of excreta in the dry state, after the admixture with them. But the comparatively high price of animal charcoal, although nearly six times the value of dry earth as a deodorant, prohibits its being extensively used. Peat is, however, cheaper than animal charcoal. To obviate the objection of cost, Mr Stanford, in 1872, proposed to make charcoal for this purpose from seaweed. The charcoal obtained from this source is said to be cheap and of great service as an excretal deodoriser. The mixed charcoal and sewage is sufficiently odourless to be stored for some months in a convenient receptacle outside a dwelling-house.

After the seaweed charcoal has become thoroughly impregnated with fæces and urine, the mixture is recarbonised in a retort, and the carbon can be again used; the distilled products (ammoniacal liquor, containing acetate of lime, tar, and gas) are sufficient to pay the cost, and it is said even to yield a profit.[158]

[Footnote 158: About the same time carbonisation of sewage in retorts, with or without previous admixture with charcoal, was proposed by Mr Hickey, of Darjeeling. There can be little doubt that, regarded in a purely sanitary point of view, carbonisation of sewage matter is an excellent plan. Mr Hickey proposed the utilisation of the ammoniacal products resulting from his process.]

_d._ _Dried earth._ The Rev. Mr Moule was the first to direct attention to the value of dried earth as a deodorant of excreta.

Mr Moule’s ‘earth closet’ consists of a box with a receptacle below for the excreta. By pulling a plug dried earth, which is placed in a hopper above, enters the closet and falls upon the excreta, thus disinfecting and deodorising it. The consumption of earth averages from 1-1/4 to 1-1/2 lb. a day. The slop water should not be thrown into the closet, but disposed of in some other way. In another plan, as in Taylor’s improved closet, the urine is carried off without mixing at all with the fæces.

Clay, marl, and vegetable humus form the best kind of earths. When dried the clay may be easily reduced to powder. Chalk and sand are comparatively useless. The receptacle is emptied from time to time, the contents forming a valuable manure.

The earth closet is more particularly adapted for small villages and isolated mansions. One difficulty of its application by cottagers consists in the necessity of collecting, drying, and storing the earth; the cottager’s mostly limited space in his dwelling not permitting this. One great obstacle to the effective carrying out of this system amongst extensive communities is the difficulty of procuring the large supply of earth that its adoption necessitates. With proper supervision and care the ‘earth system’ answers admirably; but if these are not bestowed on it, it as signally fails. It has been adopted with great success in many schools, barracks, and other large buildings.

“It is coming into great use in India, and is carried out with great attention to detail. In those European stations where water is not procurable Mr Moule’s invention has been a boon of great value, and medical officers say that nothing has been done in India of late years which has contributed so much to the health and comfort of the men. The plan of separating the urine from the fæces has been strongly advocated by Dr Cornish, of Madras, and would, no doubt, be attended with great advantages in India if there are means of disposal of the urine. The chief difficulty in the European barracks in India is felt during the rainy season, when the mixed excreta and earth cannot be kept sufficiently dry. In the case of natives of India, however, a serious difficulty arises in the use of the earth system, in consequence of the universal use of water for ablution after using the closet. Every native takes with him a small vessel holding ten to twenty ounces of water, so that a large amount of fluid has to be disposed of. The usual earth closet does not suffice for this. Mr Charles Turner, C.E., of Southampton, has contrived a closet suitable for the native family; it is unfortunately too costly, and possibly a simple iron box, with a pipe to carry off the urine and ablution water, would be better suited for the poorer classes.”[159]

[Footnote 159: Parkes.]

_e._ _Captain Lieurnur’s pneumatic plan._ This process, the invention of a Dutch engineer, is in use at Amsterdam, Leyden, Drodrecht, and a few other Continental towns. It is also known as the ‘aspiration plan.’ Its outlines are as follows:——“The pipes and, tubes leading from the various water-closets and privies peculiar to the system are connected with street mains, which mains again communicate with underground horizontal cast-iron cylinders or tanks, these tanks being directly connected with a powerful air-pump worked by steam. Communication between the main and the tanks, as well as between the tanks and the pump, can be made or broken by means of stopcocks. Hence it follows that when access is allowed between one of the tanks and the air-pump, this latter will, when put into action, produce a vacuum in the tank, and if the stopcock of the main leading to the tank be then opened, the contents of all the privies and water-closets, the pipes of which run into the main, will be removed by being swept into the tank by pneumatic force. In this manner each tank is treated in succession. Similarly the sewage is carried to the large reservoirs of a manure manufactory. It is here mixed with a little sulphuric acid to prevent the formation of ammonia, and being evaporated down _in vacuo_ becomes converted, when sufficiently dry, into poudrette. In Lieurnur’s process all deodorants are dispensed with, and its mixture with water is prevented by means of porous drain pipes laid above the sewers, by which contrivance the subsoil water is kept out of the sewers.

=Sewage, Utilisation of.= “Mr Peregrine Birch read before the Institution of Surveyors a paper on ‘The Use of Sewage by Farmers,’ which embodied some facts that deserve to be noticed, as bearing on a question we have repeatedly discussed. It appears that there are at the present time ‘upwards of one hundred owners and occupiers of land in Great Britain who use sewage for the sake alone of what they can get out of it by agricultural means.’ Of these ‘more than sixty are tenant farmers, who continue to use it although they have, annually at least, the option of ceasing to do so,’ It seems five out of six of the tenant farmers purchase the sewage they employ, so that their adhesion to the method proves conclusively that it _pays_. Nearly four thousand acres of land are under regular cultivation with sewage. Mr Birch is of opinion that ‘advocates of sewage precipitation processes should not regard sewage farmers as their rivals, for a chemical process might be very largely used with advantage when farmers are being persuaded or taught to use sewage. But this should be the distinct aim of all cultivation, for there is no chemical process that could not be worked to greater advantage during two months of the year than twelve, or applied to a small quantity of sewage at less cost than to a large.’ Our primary interest is to see the utilisation of sewage generally adopted; the method employed must be determined by experience on the grounds of cheapness and expediency.”——_Lancet._

=SHAD′DOCK.= A large species of orange, the fruit of _Citrus Decumana_ (Linn.).

=SHAGREEN′.= This is prepared from the skins of the horse, wild ass, and camel, as follows:——The skin, freed from epidermis and hair by soaking in water, and, after dressing with the currier’s fleshing-knife, is sprinkled over, whilst still wet and stretched, with the seeds of a species of chenopodium, which are imbedded in it by strong pressure, and in this state it is dried; the seeds are then shaken off, and the surface rubbed or shaved down, nearly to the bottom of the seed-pits or indentations; it is next soaked in water, by which the skin swells, and the recently depressed surface rises into a number of minute prominences; it is, lastly, dyed and smoothed off. Black is given to it with galls and copperas; blue, with a solution of indigo; green, with copper filings and sal ammoniac; and red, with cochineal and alum. Shagreen was formerly very extensively used for covering the cases of watches, spectacles, surgical instruments, &c.

=SHALLOT′.= _Syn._ ESCHALOT. The _Allium ascalonicum_ (Linn.), a plant allied to the onion, the bulb of which is much used as a sauce or pot-herb.

=SHAMPOO′ING.= A practice common in the East, having for its object the increase or restoration of the tone and vigour of the body, or the mitigation of pain. It is applied either in the bath or immediately after quitting it, generally the latter, and consists in pressing and kneading the flesh, stretching and relaxing the knee-joints, and laboriously brushing and scrubbing the skin.

=SHARPS.= See FLOUR.

=SHA′VING.= The following are Mr Mechi’s instructions for this, to many persons, troublesome operation:——Never fail to well wash your beard with soap and cold water, and to rub it dry, immediately before you apply the lather, of which the more you use the easier you will shave. Never use warm water, which makes a tender face. Place the razor (closed, of course) in your pocket, or under your arm, to warm it. The moment you leave your bed is the best time to shave. Always put your shaving-brush away with the lather on it.

The razor (being only a very fine saw) should be moved in a sloping or sawing direction, holding it nearly flat to your face, care being taken to draw the skin as tight as possible with the left hand, so as to present an even surface and throw out the beard. The practice of pressing on the edge of a razor in stropping generally rounds it; the pressure should be directed to the back, which must never be raised from the strop. If you shave from heel to point of the razor, strop it from point to heel; but if you begin with the point, then strop from heel to point. If you only once put away your razor without stropping or otherwise cleaning the edge, you must no longer expect to shave well, the soap and damp so soon rust the fine teeth or edge. A piece of plate leather should always be kept with the razors.

=SHAVING FLUID.= See ESSENCE OF SOAP.

=SHAWLS, To Scour.= Scrape one pound of soap into thin shavings, and let it be boiled with as much water as will convert into a thin jelly. When cold, beat it with the hand, and mix with it three tablespoonfuls of oil of turpentine, and one of hartshorn. Let the shawl be well washed in this mixture, and afterwards rinsed in cold water, so as to get rid of all the soap.

Next let the shawl be rinsed in salt and water, then wring out the water from it, and fold it between two sheets, being careful not to allow two folds of the shawl to lie together; finally mangle, and iron with a cool iron.

=SHEEP.= _Syn._ OVIS, L. The _Ovis aries_, an animal domesticated almost everywhere. Its flesh supplies us with food, its skin with leather, its fleece with wool, and its intestines with catgut. Its fat (sevum) is officinal. See MUTTON, SUET, &c.

=Sheep Washes.= 1. Arsenious acid in powder, carbonate of potash, of each 6 oz.; water, 14 gall. Boil together for half an hour.

2. Arsenious acid in powder, soft soap, and carbonate of potash, of each 6 oz.; sulphur, 4 oz.; bruised hellebore root, 2 oz.; water, 14 gall. Boil the ingredients in a portion of the water for half an hour, or until the arsenic is dissolved, then add the remainder of the water, and strain through a coarse sieve. Mr Youatt says:——“More care than is usually taken should be exercised in order that the fluid may penetrate to every part of the skin, and which should be ensured by a previous washing in soap and water. The arsenic that necessarily remains about the wool when the water has dried away would probably destroy the acari as fast as they are produced. When a greater quantity of arsenic has been used, or the sheep has been kept too long in the water, fatal consequences have occasionally ensued.”

3. A sheep-dipping composition employed on the Continent is:——Arsenious acid, 1 lb.; sulphate of zinc, 10 lbs.; dissolved in 25 gallons of water.

4. The Australian sheep farmers use a weak solution of bichloride of mercury (1 oz. of the bichloride to 4 gall. of water).

5. Water, 40 parts, at the temperature of 50° to 57° C.; to this add 1 part of soluble glass (the soluble silicates). This is recommended as a very efficient and perfectly safe sheep wash by Messrs Baerle and Co., of Worms. In washing the sheep with this preparation care should be taken to cover the eyes of the animal with a bandage, to perform the washing with the solution instantaneously, and to remove the surplus with tepid water.

“Yards into which newly clipped sheep are to be turned should be previously cleared of all green food, hay, and even fresh water; if perfectly empty they are still safer. When the dipping is finished they should be cleaned, washed, and swept, and any of the unused dipping solution at once poured down the drains. Dipped sheep should remain, if possible, in an open exposed place, as on a dry road, or in a large open yard. Over-crowding should be avoided, and every facility given for rapid drying, which is greatly expedited by selecting for the operation fine, clear, drying weather. On no account should sheep be returned to their grazings until they are dry, and all risk of dripping over.[160]

[Footnote 160: Finlay Dunn.]

=SHELL-FISH.= The common name for the Crustacean and Molluscous animals that are used for food. ‘Shell-fish’ are extremely liable to disturb the functions of the stomach and bowels. The oyster (_Ostrea edulis_), and the cockle (_Cardium edule_), are, perhaps, the least objectionable. The crab (_Cancer pagurus_), the crayfish (_Astacus fluvialis_), the lobster (_Homarus vulgaris_), the mussel (_Mytilus edulis_), the prawn (_Palæmon serratus_), the periwinkle (_Littorina littorea_), and the shrimp (_Crangon vulgaris_), with the exception of the claws of the first three, are always suspicious, particularly in hot weather, and often absolutely poisonous. We have seen the most alarming, nay, fatal symptoms, follow the use of mussels, even amongst those habitually accustomed to take them; whilst it is a well known fact that the luscious bodies of the crab and lobster have too often formed the last supper of the epicure. See OYSTER, &c.

=SHEL-LAC.= See LAC.

=SHELLS (Prepared).= _Syn._ TESTÆ PRÆPARATÆ (Ph. L. 1836), L. _Prep._ (Ph. L. 1836.) Wash oyster-shells (OSTRÆ——Ph. L.) with boiling water, having previously freed them from extraneous matters; then prepare them in the manner directed for chalk. The product is similar in constitution and properties to prepared chalk.

=Shells, To Polish.= 1. The surface of the shell should be first cleaned by rubbing it over with a rag dipped in hydrochloric acid, till the outer dull skin is removed. It must be then washed in warm water, dried in hot sawdust, and polished with chamois leather. Those shells which are destitute of a natural polished surface, may be either varnished or rubbed with a mixture of tripoli powder and turpentine applied by means of a wash-leather, after which fine tripoli alone should be used, and, finally, a little olive oil, the surface being brought up with the chamois leather as before.

2. “The shells are first boiled in a strong solution of potash, then wound on wheels, sometimes through one strata to show an underlying one, then polished with hydrochloric acid and putty powder. In this operation the hands are in great danger. Shell grinders are generally almost all cripples in their hands. (Spon.)

=SHER′BET.= [Pers.] A cooling drink, used in the East, prepared with the juices of fruit, and water, variously sweetened and flavoured. The word has been, of late years, commonly employed in these countries in a similar manner. See LEMONADE, ORANGEADE, and POWDERS.

=SHER′RY.= _Syn._ SHERRY WINE, SHERRIS; VINUM XERICUM (Ph. L.), VINUM ALBUM (Ph. E.), VINUM ALBUM HISPANICUM (Ph. D.), L. This is the only wine ordered in the British Pharmacopœias. See WINES.

=SHERRY-COBBLER.= _Prep._ (Redwood.) Half fill a tumbler with clean pounded ice; add a table-spoonful of powdered white sugar, a few thin slices of lemon with the peel (or some strawberries or other similar fruit, bruised), and a wine-glassful or more of sherry wine; mix them together (lightly), and as the ice melts, suck the liquor through a straw (or a small tube of silver or glass).

_Obs._ A favourite American drink; very refreshing in hot weather.

=SHIN′′GLES.= _Syn._ ZOSTER, HERPES ZOSTER, HERPES ZONA, L. A local variety of herpes or tetter, remarkable for forming a kind of belt round or partly round some part of the trunk of the body, chiefly the waist or abdomen. See TETTERS.

=SHODDY.= The epithet (we believe of American origin) is applied to the old, used-up wool and cloth, fraudulently mixed with fresh woollen fabrics. A plan for the examination of a fabric suspected of containing shoddy has been given by a German chemist, Herr Schlesinger, and is as follows:——Examine it with the microscope and note if it contains cotton, silk, or linen, as well as wool. If so dissolve them by ammoniacal solution of copper. A qualitative examination is thus obtained. Then direct attention to the wool. In shoddy both coloured and colourless fibres are often seen, the fibres having been derived from different cloths which have been partially bleached; the colouring matter, if any, instead of consisting of one pigment, will be composed of two or three different kinds, such as indigo, purpurin, or madder. Again, the diameter of the wool is never so regular as in fresh wool, but is seen to vary suddenly or gradually in diameter, and suddenly widens again with a little swelling, and tapers off again, besides which the cross markings or scales are almost always absent. When shoddy-wool is placed in liquor potassæ it is much more speedily attacked than new wool.

=SHOT METAL.= _Prep._ From lead, 1000 parts; arsenic, 3 parts. When the lead is coarse, 6 to 8 parts of metallic arsenic are required to fit it for this purpose.

=SHOW BOTTLES.= The large ornamental carboys and jars filled with coloured liquids, and displayed in the shop-windows of druggists, may be noticed under this head. They are striking objects when the solutions they contain are bright and of a deep pure tint, especially at night, when they are seen by transmitted light. The following formulæ for the solutions have been recommended by different persons:——

AMBER. From dragon’s blood (in coarse powder), 1 part; oil of vitriol, 4 parts; digest, and, when the solution is complete, dilute the mixture with distilled or soft water, q. s.

BLUE.——_a._ From blue vitriol, 2 oz.; oil of vitriol, 1/2 oz.; water, 1 pint.——_b._ A solution of indigo in sulphuric acid, diluted with water, q. s.——_c._ A solution of soluble Prussian blue in either oxalic or hydrochloric acid, slightly diluted, and afterwards further diluted with water to the proper shade of colour.

CRIMSON.——_a._ From alkanet root, 1 oz.; oil of turpentine, 1 pint. Used chiefly for the bull’s eyes of lamps.——_b._ As PINK (_b_), _below_.

GREEN.——_a._ From sulphate of copper, 2 oz.; bichromate of potash, 1 dr., or q. s.; water, 1 pint.——_b._ A solution of sulphate of copper, 2 oz.; chloride of sodium, 4 oz.; water, 1 pint, or q. s.——_c._ A solution of distilled verdigris in acetic acid, diluted with water, q. s.——_d._ Dissolve blue vitriol in water, and add nitric acid until it turns green.

LILAC.——_a._ Dissolve crude oxide of cobalt (zaffre) in nitric or hydrochloric acid, add sesquicarbonate of ammonia, in excess, and afterwards sufficient ammonio-sulphate of copper to strike the colour.——_b._ As the purple, but more diluted.

MAGENTA. Acetate of rosaniline, dissolved in water, q. s.

OLIVE. Dissolve sulphate of iron and oil of vitriol, equal weights, in water, and add of nitrate of copper, q. s. to strike the colour.

ORANGE.——_a._ A solution of bichromate of potash in water, either with or without the addition of some hydrochloric or sulphuric acid.——_b._ Dissolve gamboge or annotta in liquor of potassa; dilute with water, and add a little spirit.

PINK.——_a._ To a solution of chloride or nitrate of cobalt, in water, add sesquicarbonate of ammonia, q. s. to dissolve the precipitate at first formed.——_b._ From madder (washed with cold water), 1 oz.; sesquicarbonate of ammonia, 4 oz.; water, 3 pints; digest, with agitation, for 24 hours, then dilute with more water, and filter.

PURPLE.——_a._ A solution of sulphate of copper, 1 oz., in water, 1 quart, or q. s., with the addition of sesquicarbonate of ammonia, 1-1/2 oz.——_b._ To the last add a sufficient quantity of the first pink (_above_) to turn the colour.——_c._ To an infusion of logwood, add carbonate of ammonia or of potassa, q. s.——_d._ Sugar of lead, 3 oz.; powdered cochineal, 1 dr.; water, q. s.——_e._ Add sulphate of indigo, nearly neutralised with chalk, to an infusion of cochineal, till it turns purple.

RED.——_a._ Dissolve carmine in liquor of ammonia, and dilute with water.——_b._ Digest powdered cochineal in a weak solution of ammonia or of sal ammoniac, and afterwards dilute with water.——_c._ Add oil of vitriol, 4 oz., to water, 1 gall., and digest dried red rose leaves, 8 oz., in the mixture for 24 hours.——_d._ Dissolve madder lake in a solution of sesquicarbonate of ammonia, and dilute the solution with water.

VIOLET. To a solution of nitrate of cobalt in a solution of sesquicarbonate of ammonia, add solution of ammonio-sulphate of copper, q. s. to strike the colour.

YELLOW.——_a._ A solution of sesquioxide or rust of iron, 1/2 lb., in hydrochloric acid, 1 quart, diluted with water.——_b._ To a strong decoction of French berries add a little alum.——_c._ A simple solution of chromate or bichromate of potash in distilled water.——_d._ A solution of equal parts of nitre and either chromate or bichromate of potash, in water.

_Obs._ Most of the above require filtering, which should be done through powdered glass, placed in a glass funnel, and never through paper. They usually need a second filtration, after being exposed to the light for some weeks; hence it is convenient always to make a little more of them than is required to fill the bottle, as several of them, when diluted after filtration, become again turbid. Distilled water or filtered rain water should be used.

=SHRIMP.= See SHELL-FISH.

=SHRUB.= A species of concentrated cold punch, prepared with lemon juice, spirit, sugar, and water. When the word is used in its unqualified form, RUM SHRUB is alluded to.

=Shrub, Brandy.= _Prep._ 1. Take of brandy, 1 gall.; orange and lemon juice, of each 1 pint; peels of 2 oranges; do. of 1 lemon; digest for 24 hours, strain, and add of white sugar, 4 lbs., dissolved in water, 5 pints; in a fortnight decant the clear liquid for use.

2. As RUM SHRUB (below), but using brandy.

=Shrub, Lemon.= _Syn._ LEMONADE SHRUB. Concentrated lemonade, either with or without the addition of a little spirit. Used to make lemonade or lemon sherbet.

=Shrub, Punch.= Concentrated punch, made with equal parts of spirit and water. Used to make punch.

=Shrub, Rum.= _Prep._ 1. As BRANDY SHRUB, but substituting rum for brandy.

2. Take of rum, at proof, 34 gall. (or, if of any other strength, an equivalent quantity); essential oils of orange and lemon, of each 2 oz., dissolved in rectified spirit, 1 quart; good lump sugar, 300 lbs.; dissolved in water, 20 galls.; mix well by ‘rummaging,’ and gradually and cautiously add of Seville orange juice, or of a solution of tartaric acid in water, q. s. to produce a pleasant but scarcely perceptible acidity; next ‘rummage’ well for 15 minutes, then add sufficient water to make the whole measure exactly 100 galls., and again ‘rummage’ well for at least half an hour; lastly, bung the cask down loosely, and allow it to repose for some days. In a fortnight, or less, it will usually be sufficiently ‘brilliant’ to be racked. The product is 100 galls., at 66 u. p.

_Obs._ Rum shrub is the kind in the greatest demand, and that having a slight preponderance of the orange flavour is the most esteemed. If wholly flavoured with lemon it is apt to acquire a kind of ‘dead’ or ‘musty’ flavour by long keeping. The substitution of a few gallons of brandy for a portion of the rum, or the addition, after racking, of about 1 oz. each of bruised bitter almonds, cloves, and cassia, the peels of about 2 dozen oranges, and a ‘thread’ of the essences of ambergris and vanilla, render it delicious.

=SIAL′OGOGUES.= Medicines which increase the flow of saliva. Mercurials and pellitory of Spain belong to this class.

=SICK′NESS.= Nausea and vomiting frequently arise from the use of improper food, and other articles which offend the stomach; at other times it is symptomatic of some disease, as colic, cholera, dyspepsia, head affections, incipient fever, &c.; in which case the primary affection should be attended to. Nausea lowers the pulse, contracts the small vessels, occasions cold perspiration, severe rigors, and trembling; and diminishes, as long as it lasts, the actions, and even the general powers, of life. The act of retching, and vomiting more especially, on the contrary, rouses rather than depresses, puts to flight all the preceding symptoms, and often restores the system to itself.

The best remedies or palliatives in these affections are effervescing saline draughts, either with or without the addition of a few drops of tincture of henbane, or tincture of opium. A glass of genuine lemonade, iced, or a spoonful of crushed ice in a wine-glassful of mint water, is also very serviceable. Pepsin (Bullock and Reynolds) and oxalate of cerium are said to be most valuable remedies in the sickness of pregnancy. See DRAUGHTS, PREGNANCY, SEA SICKNESS, &c.

=SIFT′ING= is to pulverulent substances what filtration is to liquids; but in this case the medium through which the substance passes is, usually, of a simpler and coarser description. Sieves are commonly employed for the purpose, which are fitted with silk or brass-wire gauze for fine purposes, and horsehair cloth, or wire netting, for coarser ones. Drum sieves are such as are furnished with covers and an enclosed space to receive the fine powder that passes through, by which dust and loss are prevented.

=SIGHT.= See VISION.

=Sight, Effect of Gaslight on.= The German Minister of Instruction has recently issued a report on the influence of gaslight on the eye. The conclusion arrived at in this report——the result of frequent conference with well-known physicians——is that no evil results follow a moderate use of gas, if the direct action of the yellow flame on the eye is prevented. For this purpose screens or shades are employed. Very great objections, however, exist to the use of zinc or lead shades, most evils affecting the eye being traceable to them. Their use, it is said, inevitably tends to blindness or inflammation, and other harmful effects. The milky-white glass shade is the best, as it distributes the light and has a grateful effect on the eyes. The burner should not be too close to the head, as congestions of the forehead and headaches result from the radiated heat. The glass plate below the gas, employed in some places, is especially useful for the purpose, as it causes an equal distribution of the light——necessary where a number are working at one burner——prevents the radiation of heat, and tends to a steady illumination by shielding the flames from currents of air. In cases of highly-inflamed eyes, dark-blue globes can be very beneficially employed. With precautions of this kind no evil effects from the burning of gas need be feared.

=SIG′NATURES (Fac-similes of).= These may be readily obtained as follows:——

1. Let the name be written on a piece of paper, and, while the ink is still wet, sprinkle over it some finely-powdered gum Arabic, then make a rim round it, and pour on it some fusible alloy in a liquid state. Impressions may be taken from the plates formed in this way, by means of printing ink and the copper-plate press.

2. By the use of transfer ink and lithography.

=SILBER LIGHT.= This light is thus described in ‘Dingler’s Polytechnic Journal,’[161]——This mode of illumination is recommended where gas cannot be had.

[Footnote 161: ccix, 79 (‘Journ. Chem. Society,’ vol. xi, new series, 1273).]

The material used is oil, which is converted into gas before combustion takes place, whereby the combustion of the wick is greatly lessened (one wick may last a year); the accumulation of impurity is obviated, and the prevention of smell completely effected. The light is regular and uniform, and of a white colour. The light, with a burner 1-1/4 inch wide, is equal to that of 28 sperm candles, each consuming 120 gr. per hour, and with one 1-3/4 inch wide a light is obtained equal to 50 such candles.

The burning apparatus consists of a row of concentrically enclosed double cylinders, perpendicularly arranged at definite intervals. The innermost cylinder contains the wick between its two walls, the hollow space in the interior serving to convey fresh air to the interior of the flame. The second cylinder conveys air to the outer side of the wick, and the third contains oil, and is in direct communication with both wick and reservoir. The mouths of all these chambers have a dome-shaped head, and form a suitable opening in this; the gas streams forth in such a manner that it comes in contact with a current of air, and thus a complete combustion is attained.

According to the nature of the oil burnt the construction is somewhat varied in its minor details. Rape oil or light hydrocarbon oils are mentioned.

=SIL′ICA.= SiO_{2}. _Syn._ SILICIC ANHYDRIDE, SILICIC ACID, SILEX, SILICEOUS EARTH†, EARTH OF FLINTS†. This exists in quartz and rock crystal in a nearly pure state. The sands of rivers and the sea-shore, flint, and almost all the scintillating stones, chiefly consist of it.

Silica occurs under two conditions——the crystalline and the amorphous. The former variety has a sp. gr. of 2·642; the amorphous of 2·2-2·3. Some of our well-known native gems and precious stones consist almost wholly of one of the above forms of silica. In agate and calcedony the two varieties are combined. Amethyst is silica, coloured purple by ferric oxide. Onyx is formed of calcedony arranged in layers of different colours. Cornelian is a red or brown variety of silica coloured with ferric oxide, whilst opal is amorphous silica combined with varying quantities of water. Silica is present in the stems of certain plants, such as wheat, many grasses, to which the shining appearance of the stems is due, &c. The Italians polish marble with the ashes of burnt straw, the usefulness of which for such a purpose depends upon the silica contained in the straw; for similar reasons the Dutch rush is thus employed. Silica also occurs in solution in many natural waters. In the geysers, or boiling springs of Iceland, it exists in large quantity.

It may be obtained in a state of absolute purity by passing gaseous fluoride of silicon into water, collecting the resulting gelatinous precipitate on a calico filter, washing it with distilled water, drying it, and heating it to redness. Another method is to precipitate a solution of silicate of soda or potassa (soluble glass) with dilute hydrochloric acid, and to treat the precipitate as before.

Nearly pure silica may also be procured by heating colourless quartz to redness, and plunging it into cold water, by which treatment the quartz is rendered so friable as to be easily reducible to fine powder. Ordinary flints, subjected to this method, are found to yield silica in a condition approaching to purity. Amorphous silica is much more easily attacked by solvents than the crystalline variety. The artificial forms of silica are all amorphous.

The test for a silicate consists in fusing the suspected body with sodic or potassic carbonate, heating the residue with acid, and evaporating to dryness. If the residue be then treated with hot water the silica remains undissolved in the form of a white powder, which will yield a colourless bead when fused with sodic carbonate upon a piece of platinum foil before the blowpipe flame. If silica be fused with borax it becomes slowly dissolved, forming a clear, colourless bead.

Chapman contests Plattner’s opinion that, when silicates are fused with phosphor salt, the ‘silica skeleton’ that results is especially due to the presence of alkalies or earthy bases.

Chapman says: “It is true enough that silicates in which these bases are present exhibit the reaction; but as other silicates——practically all, indeed——exhibit the reaction also, the inference implied in the above statement is quite erroneous.

“The opalescence of the glass arises entirely from precipitated silica.

“If some pure silica (or a silicate of any kind), in a powdered condition, be dissolved before the blowpipe flame in borax until the glass be saturated, and some phosphor salt be then added, and the blowing be continued for an instant, a precipitate of silicate will immediately take place, the bead becoming milky white (or, in the case of many silicates, opaque) on cooling. This test may be resorted to for the detection of silica in the case of silicates, which dissolve with difficulty in phosphor salt alone, or which do not give the pronounced ‘skeleton’ with that reagent.”[162]

[Footnote 162: Chapman on ‘Blow-pipe Reactions.’]

_Prop., &c._ A fine, white, tasteless, infusible powder, insoluble in all acids, after being heated, except the hydrofluoric; requires the heat of the oxyhydrogen blowpipe for its fusion; approaches the precious stones in hardness; soluble in strong alkaline solutions; its salts are called SILICATES. Sp. gr. 2·66. See GLASS, GLASS, SOLUBLE, &c.

=Silica, Hydrates of.= By pouring a dilute solution of sodium silicate into a considerable excess of hydrochloric acid the whole of the silica is retained in solution, together with the chloride of sodium formed by the action of the hydrochloric acid upon the soda. By subjecting this solution to dialysis (see DIALYSIS) the hydrochloric acid and chloride of sodium are removed, whilst the hydrate of silica is left behind, in solution, in the dialyser. Graham recommends a stratum of the liquid four tenths of an inch in depth, to be subjected for four or five days to dialysis, the water in the outer vessel to be changed every twenty-four hours.

If the solution so obtained be carefully evaporated down in a flask, and any drying of the silicic acid at the edges of the liquid being prevented, a solution may be obtained containing 14 per cent. of silica.

The solution has a very feebly acid reaction, and is without taste or colour. It cannot be preserved in the liquid state for more than a very few days, even in well-closed vessels, but becomes converted into a transparent gelatinous mass, which separates from the water. Hydrochloric acid, as well as small quantities of caustic potash or soda, retard the coagulation.

When the solution is evaporated _in vacuo_ at 59° F. over sulphuric acid, a lustrous transparent glass is left behind, which consists of 22 per cent. of water, which closely accords with the formula SiO_{2}H_{2}O.

By the action of moist air upon silicic ether a transparent glassy hydrate was obtained by Ebelmen, to which this chemist assigned the formula 2SiO_{2},3H_{2}O. Two hydrates of silica were obtained by Fuchs, one having the formula 3SiO_{2},H_{2}O, the other, 4SiO_{2},H_{2}O.

=Silicic Chloride.= _Syn._ SILICIC TETRACHLORIDE. (SiCl_{4}.) This compound is rarely, if ever, obtained by the direct method, viz. by heating silicon in chlorine, but by the following indirect process:——A paste is made of finely divided silica, oil, and charcoal, and heated in a covered crucible. The fragments of the charred substance (consisting of silica and carbon) are then placed in a porcelain tube, which is raised to a red heat in a furnace, and during the ignition of the fragments a current of dry chlorine is passed into and over them; the silicic chloride which is thus formed being made to distil over into a bent tube surrounded by a freezing mixture of ice and salt, whereby it becomes condensed.

Silicic chloride is a very voluble and strongly fuming gas, transparent and colourless, with an irritating and pungent smell. It is immediately decomposed by water into hydrochloric acid and hydrated silica, which deposits in the vessel.

=Silicic Fluoride.= _Syn._ SILICIC TETRAFLUORIDE. (SiF_{4}.) This gas is best prepared by heating in a capacious flask or retort equal parts of finely powdered fluorspar and white sand, or glass with ten or twelve times their weight of strong sulphuric acid. This gas must be collected over mercury, and in jars that are free from the least trace of moisture.

Silicic fluoride is a colourless gas, with a very pungent odour, fuming strongly in the air, and neither burning nor supporting combustion. Faraday succeeded in liquefying it under great pressure, and Natterer states that at a temperature of -220° F. it may be solidified. By water it is partially decomposed and partially dissolved, yielding silicic acid and hydrofluosilic acid.

With twice its volume of ammoniacal gas silicic fluoride combines to form a crystalline volatile. Silicic hydride has an acid reaction.

=Silicic Hydride.= (H_{4}Si?) To procure this gas silicide of magnesium is decomposed with cold diluted hydrochloric acid.

The silicide of magnesium may be prepared as follows:——Mix intimately 40 parts of fused magnesic chloride, 35 of dried sodic silico-fluoride, and 10 of fused sodic chloride; these are mixed in a warm, dry tube, with 20 parts of sodium in small fragments, and thrown into a red-hot Hessian crucible, which is immediately covered, the operation being finished when the vapours of sodium cease to burn.