Chapter VII: ARCHITECTURE, ETC.--Suggestions in Architecture.--Large (3)

Another method is to allow pupils to assist the teacher in the preparation of experiments, to call occasionally upon members of the class to come forward and give the experiment in the place of the teacher, and to encourage home work relating to experiments. This latter is often spontaneous on the part of older pupils, and can be brought about with the smaller ones by the use of a little tact; many of the toys of the present day have some scientific principle at bottom; let the teacher find out what toys his young pupils have, and encourage them to use them in a scientific way.

In whatever ways experiments be used, the class should be made to consider the following elements as important in every case:

1. The purpose of the experiment. The same experiment may be performed at one time for one purpose, at another time for another. The purpose intended should be made the prominent thing, all others being subordinated to it. Many chemical reactions, for instance, can be made to yield either one of two or more substances for study or examination, or use, while it may be the purpose of the experiment to close only one of them.

2 The apparatus. All elements should be considered. The necessary should be separated from that which may vary. In cases where the various parts must have some definite relation to the others as regards size or position, all that should be considered with care. In complex apparatus the exact office of each part should be understood.

3. A clear understanding of what happens. To this I have already referred.

4. Why it happens.

5. In what other way it might be made to happen. In chemistry almost every substance can be prepared in several different ways. The common method is in most cases made so by some consideration of convenience, cheapness, or safety. Often only one method is considered in one place in a text book. In a review, however, several methods can be associated together. Tests, uses, etc., will vary, too, and should be studied with that fact in view. In physics phenomena illustrating a given principle can usually be made to take place in several different ways. Often very simple apparatus will do to illustrate some fact for which complex and costly apparatus would be convenient. In such case the study of the experiment with that fact in view becomes important to us who need to simplify apparatus as much as possible.

6. Special precautions which may be necessary. Some experiments always work well, even in the hands of those not used to the work. Others are successful--sometimes safe, even--only when the greatest care is taken. Substances are used constantly in work in chemistry which are deadly poisons, others which are gaseous and will pass through the smallest holes. In physics the experiments usually present fewer difficulties of this sort. But special care is necessary to complete success here.

7. Other things shown by the experiment. While the main object should be kept in most prominent view in all experimental work, the fullest educational value will come only when all that can be learned by the use of an experiment is carefully considered.

In selecting just the work to be taken up with a given class of children, attention must be paid to the selection of the appropriate matter to be presented and the well adapted method of presenting it. The following points should be carefully considered:

1. The matter must be adapted to the capacity of the child. This must be true both as regards the quality and the quantity. The tendency will be to teach too much when the matter presented is entirely new, but too little in many cases where the pupil already knows the subject in a general way. Matter is valuable only when given slowly enough to permit of its being fully understood and memorized, while on the other hand method is valuable only when it secures the development of attention and the various faculties of the child's mind by presenting a sufficient amount of the new.

2. The work must be based on what is already known. This, one of the best known of the principles of teaching, is of at least as great importance in physical science as in any other department of knowledge. It seems to me in many cases to be more important here than elsewhere. It is not necessary to reach each point by passing over every other point usually considered. Lessons in electricity or sound, for instance, can be given to children who have done nothing with other parts of science. But a natural beginning must be made, and an orderly sequence of lessons adopted. Children will not do what adults would find almost impossible in covering gaps between lessons.

Science may be compared to a great temple. Pillars, each built of many curiously joined stones, standing at the very entrance, represent the departments of science so far as man has studied them. We need not dig down and study the foundations with the children; we need not study every pillar nor choose any particular one rather than some other; but we must learn something of every stone--of each great fact--in the pillar we select, be it ever so little. The original investigator climbs to stones never before reached, or boldly ventures away into the dim recesses beyond the entrance to bring back hints of what may be known and believed a hundred years hence, perhaps. The exact investigator measures each stone. Patiently and toilsomely scientific men examine them with glass and reagent. We need not do this, but we must omit none of the stones.

3. The work must be continuous. To continue the figure, the stones must be considered in some regular order. One lesson in electricity, one in sound, then one in some other department is injurious. We remember best by associated facts, and, while with the child this is less so than with the man, one great object of this work is to teach him to remember in that way.

4. Experiments should never be performed for mere show. Of two experiments which illustrate a fact equally well it is often best to select the most striking and brilliant one. The attention and interest of the child will be gained in this way when they would not be to so great an extent in any other. The point of the experiment, however, should never be lost sight of in attention to the merely wonderful in it.

With older pupils, and especially with those who use books for themselves and perform the experiments there considered, the fact that experiments demand work, downright hard work, with care, and patience, and perseverance, and courage, cannot be kept too prominently before them.

5. Every lesson should have a definite object. Not the general value of the experiment, but some _one thing_ which it shows should be the object considered.

6. Each experiment should be associated with some truth expressed in words. The experiment should be remembered in connection with a definite statement in each case. The memory of either the experiment, or the principle apart from the experiment, is a species of half knowledge which should be avoided. An unillustrated principle must, when the necessity arises, be stored in the memory; and in the systematic study of books this necessity will often come. But we should never crowd this abstract work on the memory unassisted by the suggestive concrete, when the concrete aid is possible.

7. All that is taught should be true. It is not necessary to attempt to exhaust a subject, nor to attempt to teach minute details regarding it to the pupils in our schools, but it is necessary that every statement given to the pupil to be learned and remembered should contain no element of falsehood.

The student in mathematics experiences a feeling of growing strength and power when he finds, in algebra, that the formula he used in arithmetic in extracting a square root has grown in importance by leading indirectly to a theorem of which it is only one particular case--a theorem with a more definite proof, and a larger capability for use than he had thought possible. When he finds a still simpler proof for the binomial theorem in his study of the calculus, his feeling of increasing power and the desire for still greater results deepens and intensifies. Were he to find, on the contrary, that from a false notion of the means to be used in making a thing simple, his teacher in arithmetic had taught him what is false, we should approve his feeling of disgust and disappointment. Early impressions are the most lasting, and the hardest part of school work for the teacher is the unteaching of false ideas, and the correcting of imperfectly formed and partially understood ideas. I took a case from mathematics, the exact science, to illustrate this point. But I must not neglect to notice the difference between that subject and physical science. The latter consists of theories, hypotheses, and so-called laws, supported by _observed facts_. The facts remain, but time has overthrown many of the hypotheses and theories, and it will doubtless overthrow more and give us something better and truer in their place. While a careful distinction between what is known and what is believed is necessary, I should always class the teaching of accepted theories and hypotheses with the teaching of the true.

But teachers, with more of imagination than good sense, teach distinctions which do not exist, generalizations which do not generalize, and do incalculable mischief by so doing.

8. Experimental work should be thoroughly honest as to conditions and results. If an experiment is not the success you expected it would be, say so honestly, and if you know why, explain it. The pupil should be taught to know just what _is_, theory or expectation to the contrary notwithstanding. Discoveries in physical science have often originated in a search for the reason for some unexpected thing.

The relation of the study of science to books on science should be considered. For the work done with pupils before they are given books to use for themselves, any attempt to follow a text book is to be deplored. The study of the properties of matter, for instance, would be a fearful and wonderful thing to set a class of little ones at as a beginning in scientific work. Just what matter, and force, and molecules, and atoms are may be well enough for the student who is old enough to begin to use a book, but they would be but dry husks to a younger child. Many of the careful classifications and analyses of topics in text books had far better be used as summaries than in any other way; and a definition is better when the pupil knows it is true than when he is about to find out whether it is or not.

An ideal course in science would be one in which nothing should be learned but that found out by the observation of the pupil himself under the guidance of the teacher, necessary terms being given, but only when the thing to be named had been considered, and the mind demanded the term because of a felt need. Practically such a method is impossible in its fullest sense, but a closer approach to it will be an advantage.

Among the numerous good results which will follow the study of physical science are the following:

1. The cultivation of all the faculties of the child in a natural order, thus making him grow into a ready, quick, and observing man. Education in schools is too often shaped so as to repress instead of cultivate the instinctive desire for the _knowledge of things_ which is found in every child.

2. The mechanical skill which comes from the preparation and use of apparatus.

3. The ability to follow directions.

4. The belief in stated scientific facts, the understanding of descriptions, diagrams, etc.

5. The habitual scientific use of events which happen around us.

6. The study of the old to find the new. The principle of the telephone, for instance, is as old as spoken language. The mere[1] pulses in the air--carrying all the characteristics of what you say--may set in vibration either the drum of my ear, or a disk of metal. How simple--and how simple all true science is--when we understand it.

[Transcribers note 1: corrected from 'more']

8. The cultivation of the scientific judgment, and the inventive powers of the mind. One great original investigator, made such by the direction given his mind in one of our common schools, would be cheaply bought at the price of all that the study of science in our schools will cost for the next quarter of a century.

8. Honesty. If there is a study whose every tendency is more in the direction of honesty and truthfulness--both with ourselves and with others--than is the study of experimental science, I do not know what it is.

Physical science, then, will help in making men and women out of our boys and girls. It is worthy of a fair, earnest trial everywhere.

A few minutes each day in which a class or a school study science in some of the ways I have indicated will give a knowledge at the end of a term or a year of no mean value. The time thus spent will have rested the pupils from their books, to which they will return refreshed, and instead of being time lost from other study the work will have been made enough more earnest and intense to make it again.

Apparatus for illustrating many of the ordinary facts of physics can be devised from materials always at hand. Many more can be made by any one skilled in the use of tools. In chemistry, the simplicity of the apparatus, and comparative cheapness of ordinary chemicals, make the use of a large number of beautiful and instructive experiments both easy and cheap.

A nation is what its trades and manufactures--its inventions and discoveries--make it; and these depend on its trained scientific men. Boys become men. Their growing minds are waiting for what I urge you to offer. Science has never advanced without carrying practical civilization with it--but it has never truly advanced save by the use of the experimental method. _And it never will_.

Let us then look forward to the time when our boys and young men--our girls and young women--shall extend the boundaries of human knowledge by its use, fitted so to do by what we may have done for them.

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GEOGRAPHICAL SOCIETY OF THE PACIFIC.

This society is a recent organization, the objects of which are to encourage geographical exploration and discovery; to investigate and disseminate geographical information by discussion, lectures, and publications; to establish in this, the chief maritime city of the Western States, for the benefit of commerce, navigation, and the industrial and material interests of the Pacific slope, a place where the means will be afforded of obtaining accurate information not only of the countries bordering on the Pacific ocean, but of every part of the habitable globe; to accumulate a library of the best books on geography, history, and statistics; to make a collection of the most recent maps and charts--especially those which relate to the Pacific coast, the islands of the Pacific and the Pacific ocean--and to enter into correspondence with scientific and learned societies whose objects include or sympathize with geography.

The society will publish a bulletin and an annual journal, which will interchange with geographical and other societies. Monthly meetings are to be held, at which original papers will be read or lectures be given; and to which, as well as to the entertainments to distinguished travelers, to the conversazioni, and to the informal evenings, the fellows of the society will have the privilege of introducing their friends. The initiation fee to the society is $10; monthly dues $1; life fellowship $100.

At a meeting held at the Palace Hotel on the 12th May, the following gentlemen were elected for the ensuing year: President, Geo. Davidson; Vice-Presidents, Hon. Ogden Hoffman, Wm. Lane Booker, H.B.M. Consul, and John R. Jarboe; Foreign Corresponding Sec., Francis Berton; Home Cor. Sec., James P. Cox; Treas., Gen. C. I. Hutchinson; Sec'y, C. Mitchell Grant, F.R.G.S. The council is composed of the following: Hon. Joseph W. Winans, Hon. J.F. Sullivan, Ralph C. Harrison, A.S. Hallidie, Thos. E. Stevin, F.A.G.S., W.W. Crane, Jr., W.J. Shaw, C.P. Murphy, Thos. Brice, Edward L.G. Steele, Gerrit L. Lansing, Joseph D. Redding. The Trustees are Geo. Davidson, Wm. Lane Booker, Hon. Jno. S. Hager, Geo. Chismore, M.D., Selim Franklin.

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THE BEHRING'S STRAITS CURRENTS.

It will be remembered that a short time since we mentioned the fact that W.H. Dall, of the U. S. Coast Survey, who has passed a number of years in Alaskan waters, on Coast Survey duty, denied the existence of any branch of the Kuro Shiwo, or Japanese warm stream, in Behring's Straits. That is, he failed to find evidence of the existence of any such current, although he had made careful observations. At the islands in Behring's Straits, his vessel had sailed in opposite directions with ebb and flood tide, and he thought the only currents there were tidal in their nature. The existence or non-existence of this current is an important point in Arctic research on this side of the continent.

At the last meeting of the Academy of Sciences, Prof. Davidson, of the U. S. Coast Survey, author of the "Alaska Coast Pilot," refuted Dr. Dall's opinion of the non-existence of a branch of the Kuro Shiwo, or Japanese warm stream, from the north Pacific into the Arctic Ocean, through Behring's Straits. He said that in 1857 he gave to the Academy his own observations, and recently he had conferred with Capt. C.L. Hooper, who commanded the U. S. steamer Thomas Corwin, employed as a revenue steam cruiser in the Arctic and around the coast of Alaska. Capt. Hooper confirms the opinions of all previous navigators, every one of which, except Dr. Dall, say that a branch of this warm stream passed northward into the Arctic through Behring's Strait. It is partly deflected by St. Lawrence Island, and closely follows the coast on the Alaskan side, while a cold current comes out south, past East Cape in Siberia, skirting the Asiatic shore past Kamschatka, and thence continues down the coast of China. He said ice often extended several miles seaward, from East Cape on the Asiatic side of Behring Strait, making what seamen call a false cape, and indicating cold water, while no such formation makes off on the American side, where the water is 12 degrees warmer than on the Asiatic shore off the Diomede islands, situated in the middle of Behring's Strait, the current varies in intensity according to the wind.

Frequently it is almost nothing for several days, when after a series of southerly winds the shallow Arctic basin has been filled, under a heavy pressure, with an unusual volume of water, and a sudden change to northerly winds, makes even a small current setting southward for a few days, just as at times the surface currents set out our Golden Gate continuously for 24 and 48 hours, as shown by the United States Coast Survey tide gauges. Whalers report that the incoming water then flows in, under the temporary outflowing stream.

Old trees, of a variety known to grow in tropical Japan, are floated into the Arctic basin as far as past Point Barrow, on the American side, but none are found on the Asiatic side, or near Wrangell Land, where a cold stream exists, and ice remains late in the season. On the northern side of the Aleutian islands are found cocoanut husks and other tropical productions stranded along the beaches. The American coast of Alaska has a much warmer climate than the Asiatic coast of Siberia, and the American timber line extends very far north. The ice opens early in the season on the American side, and invariably late on the Asiatic.

Capt. C. L. Hooper says that when just north of Behring's Strait, off the American coast, in the Arctic basin, the U.S. steamer Thomas Corwin, when becalmed for 24 hours, drifted 40 miles to the northward. From all these, and other facts, and the unanimous testimony of American whalemen, who have for years spent many months annually in the Arctic, and from his own observations, he argued that a branch of the Kuro-Shiwo or Japanese warm stream, unquestionably runs northward through Behring's Strait into the Arctic basin along the northwestern coast of Alaska.

Prof. Davidson then called to mind the testimony in regard to the existence of Plover Island, between Herald Island and Wrangell Land, which he said was first made public through this academy. The evidence of Capts. Williams and Thomas Long were recited and highly praised. One of the officers of Admiral Rodgers' expedition climbed to near the top of Herald Island, at a time of great refraction, when probably a false horizon existed, and hence did not see Plover Island, although Wrangell Land was in sight.

Prof. Davidson thinks all the authorities are against Dr. Dall, who attributes the warm current he observed on the American coast to water from the Yukon River and to the large expanse of shallow water exposed to the sun's rays. As Dall's observations only covered a few days of possibly exceptional weather, and the whalers and Captain Hooper's cover vastly longer periods, and whalers all say it is a pretty hard thing to beat southward through Behring's Strait, owing to the northerly current setting into the Arctic, we are forced to the conclusion that Dr. Dall has mistaken the exception for the rule, and his conclusions are therefore erroneous. When, in 1824, Wrangell went north, he, like others, always found broken ice and considerable open water. In 1867, when Capt. Thomas Long made his memorable survey of the coast of Wrangell Land, the season was an exceptionally open one, and in California we had heavy rains, extending into July.

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EXPERIMENTAL GEOLOGY.

ARTIFICIAL PRODUCTION OF CALCAREOUS PISOLITES AND OOLITES.

Mr. Stanislas Meunier communicates to _Le Nature_ an account of some interesting specimens of globular calcareous matter, resembling pisolites or peastones both in appearance and structure, which were accidentally formed as follows: The Northern Railway Company, France, desiring to purify some calciferous water designed for use in steam boilers, hit upon the ingenious expedient of treating it with lime water whose concentration was calculated exactly from the amount of lime held in the liquid to be purified. The liquids were mixed in a vast reservoir, to which they were led by parallel pipes, and by which they were given a rapid eddying motion. The transformation of the bicarbonate into neutral carbonate of lime being thus effected with the accompaniment of a circling motion, the insoluble salt which precipitated, instead of being deposited in an amorphous state, hardened into globules, the sizes of which were strictly regulated by the velocity of the currents. Those that have been formed at one and the same operation are uniform, but those formed at different times vary greatly--their diameters varying by at least one millimeter to one and a half centimeters. The surface of the smaller globules is smooth, but that of the larger ones is rough. Even by the naked eye, it may be seen that both the large and small globules are formed of regularly superposed concentric layers. If an extremely thin section be made through one of them it is found that the number of layers is very great and that they are remarkably regular (A). By the microscope, it has been ascertained that each layer is about 0.007 of a millimeter in thickness.

On observing it under polarized light the calcareous substance is discovered to be everywhere crystallized, and this suggests the question whether the carbonate has here taken the form of aragonite or of calcite. Examination has shown it to be the latter. The density of the globules (2.58) is similar to that of ordinary varieties of calcite. It is probable that if the operation were to take place under the influence of heat, under the conditions above mentioned, aragonite would be formed. It is hardly necessary to dwell upon the possible geological applications of this mode of forming calcareous oolites and pisolites.

ON CRYSTALS OF ANHYDROUS LIME.

Some time ago it was discovered that some limestone, which had been submitted for eighteen months to a heat of nearly 1,000 degrees in the smelting furnaces of Leroy-Descloges (France), had given rise to perfectly crystallized anhydrous lime. Figure C shows three of these crystals magnified 300 diameters. It will be noticed that they have a striking analogy with grains of common salt. They are, in fact, cubes (often imperfect), but do not polarize light, as a substance of the first crystalline system should. However, it is rarely the case that the crystals do not have _some_ action on light. Most usually, when the two Nicol prisms are crossed so as to cause extinction, the crystals present the appearance shown at D. That is to say, while the central portion is totally inactive there are seen on the margins zones which greatly brighten the light.

A and B.--Calcareous Pisolites and Oolites produced artificially. A.--External aspect and section of a Pisolite. B.--Details of internal structure as seen by the microscope.

C and D.--Crystals of anhydrous Lime obtained artificially. C.--Crystals seen under the microscope in the natural light. D.--Crystals seen under the microscope in polarized light.

The phenomenon is explained by the slow carbonization of the anhydrous lime under the influence of the air; the external layers passing to the state of carbonate of lime or Iceland spar, which, as well known, has great influence on polarized light. This transformation, which takes place without disturbing the crystalline state, does not lead to any general modification of the form of the crystals, and the final product of carbonization is a cubic form known in mineralogical language as _epigene_. As the molecule of spar is entirely different in form from the molecule of lime, the form of the crystal is not absolutely preserved, and there are observed on the edges of the epigene crystal certain grooves which correspond with a loss of substance. These grooves are quite visible, for example, on the crystal to the left in Fig. D.

Up to the present time anhydrous lime has been known only in an amorphous state. The experiment which has produced it in the form noted above would doubtless give rise to crystallized states of other earthy oxides likewise, and even of alkalino-earthy oxides.

COCCIDÆ.

[Footnote: A paper recently read before the California Academy of Sciences.]

By DR. H. BEHR.

With the exception of Hymenoptera there is no group of insects that interfere in so many ways in good and evil with our own interests, as that group of Homoptera called Coccidæ.

But while the Hymenoptera command our respect by an intellect that approaches the human, the Coccus tribe possesses only the lowest kind of instinct, and its females even pass the greater part of their lives in a mere vegetation state, without the power of locomotion or perception, like a plant, exhibiting only organs of assimilation and reproduction.

But strange to say, these two groups, otherwise so very dissimilar, exhibit again a resemblance in their product. Both produce honey and wax.

It is true, the honey of this tribe is almost exclusively used by the ants. But I have tasted the honey-like secretion of an Australian lecanium living; on the leaves of Eucalyptus dumosus; and the manna mentioned in Scripture is considered the secretion of Coccus manniparus (Ehrenberg) that feeds on a tamarix, and whose product is still used by the native tribes round Mount Sinai.

Several species of Coccides are used for the production of wax; many more, among which the Cochenill, for dyes.

All these substances can be obtained in other ways, even the Cochenill is to a great extent superseded by aniline dyes, but in regard to one production, indispensable to a great extent, we are entirely dependent on some insects of this family; it is the Shellac, lately also found in the desert regions around the Gila and Colorado on the Larrea Mexicana. You will remember that excellent treatise on this variety of Shellac, written by Professor J.M. Stillman at Berkeley, on its chemical peculiarities.

But all these different forms of utility fall very lightly in weight, and can not even be counted as an extenuating circumstance, when we compare them to the enormous evils brought on farmer and gardener by the hosts of those Coccides that visit plantations, hothouses, and orchards.

To combat successfully against these insect-pests we have first to study their habits and then adapt to them our remedies, which you will see are more effective when well administered than those which we possess against insect pests of other classes.

I give here only the outlines of their natural history, peculiarities that are common to all, for it would be impossible to go into detail. Where there are exceptions of practical importance I will mention them.

In countries with a well defined winter the winged males appear as soon as white frosts are no more usual, and copulate with the unwieldy limbless female, that looks more like a gall or morbid excrescence, than a living animal. Shortly after the young ones are perceptible near the withered body of their mother, covered by waxy secretions that look somewhat like a feathery down.

These young ones are lively enough, they move about with agility, and it is not till high summer that they fasten themselves permanently, and lose feet and antennae, organs of locomotion and perception that are no more of any use to them. (There is a slight difference in this regard between different genera, as for instance, Coccus and Dorthesia retain these organs in different degrees of imperfection, Lecanium and Aspidiotus losing every trace of them.)

In this limbless, senseless state the females remain fall and winter. Toward the end of winter these animated galls begin to swell, and those containing males enter the state of the chrysalis, from which the males emerge at the beginning of the warm season and fecundate the gall-like females, which undergo neither chrysalis state nor any other change, but die, or we may call it dissolve into their offspring, for there scarcely remains anything of them, except a pruinous kind of down, after having given birth to the young ones.

Now we come to the practical deduction from these facts. It is clear that the only time when the scalebug can emigrate and infest a new tree is the time when it is a larva, that is, when it has the power of locomotion. In countries with a pronounced winter this time begins much later than with us, but it ends about the same time, that is, the beginning of August. I have seen the male of Aspidiotus in February, so that the active larva may be expected in March, and the active Lecanium Hesperidum I have seen last year, June 27, at Colonel Hooper's ranch in Sonoma County. We may safely fix the time of the active scalebug from March to August.

Notwithstanding the agility of the young scalebug, the voyage from one tree to another, considering the minute size of the traveler, is an undertaking but seldom succeeding, but one female bug, if we take into account its enormous fertility, is sufficient to cover with its grandchildren next year a tree of moderate size.

Besides there is another and much more effective way of transmigration by the kind assistance of the ant who colonizes the scalebug as well for its wax as it colonizes the Aphis for its honey. Birds on their feathers and the gardener himself on his dress contribute to spread them.

But even the ant can not transplant the scalebug when it is once firmly fixed by its rostrum.

It is evident, therefore, that the time for the application of insecticides is the time when all the scalebugs are fixed, that is about the end of July or beginning of August. All previous application will clean the tree or plant only for a time, and does not prevent a more or less numerous immigration from the neighboring vegetation, especially if an ant-hill is not far off.

As to the insecticide, there are to be applied two very effective ones, each with its advantages and disadvantages.

1. Petroleum and its different preparations.

2. Lye or soap.

The petroleum is the best disinfectant. It can safely be applied to any cutting or stem, as long as it is not planted, but is one of the most invidious substances when applied to vegetation in the garden, or fields. If effectively applied, it can not be prevented from running down the bark of the tree and entering the ground, where every drop binds a certain amount of earth to an insoluble substance, in which state it remains for ever. With every application the quantity of these insoluble compounds is augmented and sterility added.

If I am not mistaken, it was near Antwerp--at least I am certain it was in Belgium--where the first experience of this kind is recorded.

In France, preparations of coal tar have been recommended and have been lately used in the form of a paint. May be that in this form the substance is not so apt to enter into combinations with the soil. At any rate, the method is of too recent a date to permit any conclusions about the final result of these applications, as the invidious nature of the substance produces, by gradual accumulation, its effects, which are not perceived until they are irreparable.

2. Lye or soap. The application of these insecticides requires more care, and is therefore more troublesome. But instead of attracting fertility from the soil, they add to it. In Southern Europe soap and water has been for many years the remedy against the Lecanium Hesperidum. The method applied by the farmers in Portugal, as described to me by Dr. Bleasdale, is perhaps the most perfect one. The Portuguese have very well observed that the colonization of scalebugs always begins at the lowest end of the trunk and pretend, therefore, that the scalebug comes out of the ground. This, of course, is not the case, but may their interpretation be an error, they have been practical enough in utilizing their observation about the invasion beginning near the roots. They knead a ring of clay round the tree, in which ring the soap water runs when they wash the tree, and besides, they fill frequently the little ditch formed by this ring.

This arrangement of course is only possible in climates of a rainy summer.

As it is our object to make our knowledge as available as possible for practical purposes, I repeat for the benefit of cultivators the advice, without repeating the reasoning:

1. Use the petroleum for disinfecting imported trees and cuttings:

2. Use soap for cleaning trees planted in your orchard.

3. If you must use the petroleum in your garden, use it in August, when a single application is sufficient.

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AGRICULTURAL ITEMS.

The exportation of dried apples from this country to France has greatly increased of late years, and now it is said that a large part of this useful product comes back in the shape of Normandy cider and light claret.

A.B. Goodsell says in the _New York Tribune_: "Put your hen feed around the currants. I did this twice a week during May and June, and not a currant worm was seen, while every leaf was eaten off other bushes 150 feet distant, and not so treated."

Buckwheat may be made profitable upon a piece of rough or newly cleared ground: No other crop is so effective in mellowing rough, cloddy land. The seed in northern localities should be sown before July 12; otherwise early frosts may catch the crops. Grass and clover may sometimes be sown successfully with buckwheat.

The London News says: "Of all poultry breeding, the rearing of the goose in favorable situations is said to be the least troublesome and most profitable. It is not surprising, therefore, that the trade has of late years been enormously developed. Geese will live, and, to a certain extent, thrive on the coarsest of grasses."

When a cow has a depraved appetite, and chews coarse, indigestible things, or licks the ground, it indicates indigestion, and she should have some physic. Give one pint and a half of linseed oil, one pound of Epsom salts, and afterward give in some bran one ounce of salt and the same of ground ginger twice a week.

Asiatic breeds of fowl lay eggs from deep chocolate through every shade of coffee color, while the Spanish, Hamburg, and Italian breeds are known for the pure white of the eggshell. A cross, however remote, with Asiatics, will cause even the last-named breeds to lay an egg slightly tinted.

In setting out currant bushes care should be exercised not to place any buds under ground, or they will push out as so many suckers. Currants are great feeders, and should be highly manured. To destroy the worm, steep one table-spoonful of hellebore in a pint of water, and sprinkle the bushes. Two or three sprinklings are sufficient for one season.

Mr. Joseph Harris, of Rochester, makes a handy box for protecting melons and cucumbers from insect enemies. Take two strips of board of the required size, and fasten them together with a piece of muslin, so the muslin will form the top and two sides of the box. Then stretch into box form by inserting a small strip of wood as a brace between the two boards. This makes a good, serviceable box, and, when done with for the season, it can be packed into a very small space, by simply removing the brace and bringing the two board sides together. As there is no patent on the contrivance, anybody can make the boxes for himself.

Mr. C. S. Read recently said before the London Fanners' Club: "American agriculturists get up earlier, are better educated, breed their stock more scientifically, use more machinery, and generally bring more brains to bear upon their work than the English farmer. The practical conclusion is, that if farmers in England worked hard, lived frugally, were clad as meanly as those of the States, were content to drink filthy tea three times a day, read more and hunted less, the majority of them may continue to live in the old country."--_N. E. Farmer_.

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TIMBER TREES.

A paper was read by Sir R. Christison at the last meeting of the Edinburgh Botanical Society upon the "Growth of Wood in 1880." In a former paper, he said, he endeavored to show that, in the unfavorable season of 1879, the growth of wood of all kinds of trees was materially less than in the comparatively favorable season of 1878. He had now to state results of measurements of the same trees for the recent favorable season of 1880. The previous autumn was unfavorable for the ripening of young wood, and the trees in an unprepared condition were exposed during a great part of December, 1879, to an asperity of climate unprecedented in this latitude. This might have led one to expect a falling off in the growth of wood, and it appeared, from comparison of measurements, that, with very few exceptions, the growth of wood last year was even more below the average of favorable years than that of the bad year, 1879. Thus, in fifteen leaf-shedding trees of various species, exclusive of the oak, the average growth of trunk girth in three successive years was: 1878, 8-10ths; 1879, 45-100ths; 1880, 3-10ths and a half. In four specimens of the oak tribe, the growth was: 1878, 8-10ths; 1879, 77-100ths; 1880, 54-100ths. In twenty specimens of the evergreen Pinaceae the growth was: 1878, 8-10ths; 1879, 7-10ths; 1880, 6-10ths and a half. After giving details in regard to particular trees, Sir Robert stated, as general deductions from his observations, that leaf-shedding trees, exclusive of the oak, suffered most; that the evergreen Pinaceae suffered least; and that there was some power of resistance on the part of the oak tribe which was remarkable, the power of resistance of the Hungary oak being particularly deserving of attention. In another communication on the "extent of the season of growth," Sir Robert stated, as the result of observations on five leaf-shedding and five evergreen trees, that in the case of the former, even in a fine year, the growth of wood was confined very nearly, if not entirely, to the months of June, July, and August; while in the case of the latter growth commenced a month sooner, terminating, however, about the same time. Mr. A. Buchan said it was proposed that the inquiry should be taken up more extensively over Scotland.

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MEDICAL USES OF FIGS.--Prof. Bouchut speaks (_Comptes Rendus_) of some experiments he has made, going to show that the milky juice of the fig-tree possesses a digestive power. He also observed that, when some of this preparation was mixed with animal tissue, it preserved it it from decay for a long time. This fact, in connection with Prof. Billroth's case of cancer of the breast, which was so excessively foul smelling that all his deodorizers failed, but which, on applying a poultice made of dried figs cooked in milk, the previously unbearable odor was entirely done away with, gives an importance to this homely remedy not to be denied.--_Medical Press and Circ._

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BLOOD RAIN.

The sensibilities of ignorant or superstitious people have at various times been alarmed by the different phenomena of so-called blood, ink, or sulphur rains. Ehrenberg very patiently collected records of the most prominent instances of these, and published them in his treatise on the dust of trade winds. Some, it is known, are due to soot; others, to pollen of conifers or willows; others, to the production of fungi and algae.

Many of the tales of the descent of showers of blood from the clouds which are so common in old chronicles, depends, says Mr. Berkeley, the mycologist, upon the multitudinous production of infusorial insects or some of the lower algae. To this category belongs the phenomenon known under the name of "red snow." One of the most peculiar and remarkable form, which is apparently virulent only in very hot seasons, is caused by the rapid production of little blood-red spots on cooked vegetables or decaying fungi, so that provisions which were dressed only the previous day are covered with a bright scarlet coat, which sometimes penetrates deeply into their substance. This depends upon the growth of a little plant which has been referred to the algae, under the name of _Palmellae prodigiosa_. The rapidity with which this little plant spreads over meat and vegetables is quite astonishing, making them appear precisely as if spotted with arterial blood; and what increases the illusion is, that there are little detached specks, exactly as if they had been squirted from a small artery. The particles of which the substance is composed have an active molecular motion, but the morphosis of the production has not yet been properly observed. The color of the so-called "blood rain" is so beautiful that attempts have been made to use it as a dye, and with some success; and could the plant be reproduced with any constancy, there seems little doubt that the color would stand. On the same paste with the "blood-rain" there have been observed white, blue, and yellow spots, which were not distinguishable in structure and character.

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TOPICAL MEDICATION IN PHTHISIS.

Dr. G.H. Mackenzie reports in the _Lancet_ an acute case of phthisis which was successfully treated by him by causing the patient to respire as continuously as possible, through a respirator devised for the purpose, an antiseptic atmosphere. The result obtained appears to bear out the experiments of Schüller of Greifswald, who found that animals rendered artificially tuberculous were cured by being made to inhale creosote water for lengthened periods. Intermittent spraying or inhaling does not produce the same result. In order to insure success the application to the lungs must be made _continuously_. For this purpose Dr. Mackenzie has used various volatile antiseptics, such as creosote, carbolic acid, and thymol. The latter, however, he has discarded as being too irritating and inefficient. Carbolic acid seems to be absorbed, for it has been detected freely in the urine after it had been inhaled; but this does not happen with creosote. As absorption of the particular drug employed is not necessary, and therefore not to be desired, Dr. Mackenzie now uses creosote only, either pure or dissolved in one to three parts of rectified spirits. "Whether," says he, "the success so far attained is due to the antidotal action of creosote and carbolic acid on a specific tubercular neoplasm, or to their action as preventives of septic poisoning from the local center in the lungs, it is certain that their continuous, steady use in the manner just described has a decidedly curative action in acute phthisis, and is therefore, worthy of an extended trial."

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ON THE LAW OF AVOGADRO AND AMPERE.

The Scientific American Supplement of May 14,1881, contains, under this head, Mr. Wm. H. Greene's objections to my demonstration (in No. 270 of the same paper) of the error of Avogadro's hypothesis. The most important part of my argument is based on the evidence afforded by the compound cyanogen; and Mr. Greene, directing his attention to this subject in the first place, states that because cyanogen combines with hydrogen or with chlorine, without diminution of volumes, I have concluded that the hypothesis falls to the ground. This statement has impressed me with the conviction that Mr. Greene has failed to perceive the difficulty which is at the bottom of the question, and I will, therefore, present the subject more fully and comprehensively.

The molecule of any elementary body is, on the ground of the hypothesis, assumed to be a compound of two atoms, and the molecule of carbon consequently C_2=24; that of nitrogen N_2=28. Combination of the two, according to the same hypothesis, takes place by substitution; the atoms are supposed to be set free and to exchange places, forming a new compound different from the original only in this: that each new particle contains an atom of each of the two different substances, while each original particle consists of two identical atoms. The product is, therefore, assumed to be, and can, under the circumstances, be no other than particles of the composition CN and weight 26. These particles are molecules, according to the definition laid down, just as C_2 and N_2; but there is this essential difference, that the specific gravity of cyanogen gas, 26, coincides with the molecular weight, while the assumed molecular weight, N_2=28, is twice as great as the specific gravity of the gas, N=14.

In using the term molecular weight, it is to be remembered that it does not express the weight of single molecules, but only their relative weight, millions of millions molecules being contained in the unit of volume. But on the hypothesis that there is the same number of molecules in the same volume of any gas, the specific gravities of gases can be, and are, identified with their molecular weights, and, on the ground of the hypothesis again, the unit of the numbers which enter into every chemical reaction and constitute the molecular weight, is stipulated to be that contained in two volumes.

The impossibility of the correctness of the hypothesis is now revealed by the fact just demonstrated, that in the case of nitrogen the specific gravity does not coincide with the molecular weight. If equal volumes contain the same number of molecules, the specific gravities and the molecular weights must be the same; and if the specific gravities and molecular weights are not the same, equal volumes cannot contain the same number of molecules. The assumed molecular weight of nitrogen is twice as great as the specific gravity, but the molecular weight and the specific gravity of cyanogen are identical; the number of molecules contained in one volume of cyanogen must, therefore, necessarily be twice as great as the number contained in one of nitrogen, and this is fully and completely borne out by the chemical facts.

In saying that when cyanogen combines with chlorine there is naturally no condensation, Mr. Greene has no idea that this natural law is fatal to his artificial law of Avogadro and Ampere; "for," continues he, "the theory is fulfilled by the actual reaction." It is not. The theory requires two vols. of cyanogen and two vols. of chlorine, that is, the unit of numbers, to enter into reaction and to produce two vols. of the compound. But they produce four vols., and the non-condensation is therefore in opposition to the theory. It is true beyond doubt that the molecular weight of cyanogen chloride is contained in two volumes, in spite of the hypothesis, not on the ground of it; two vols. + two vols., producing four vols.; two vols. could, theoretically, contain only half the unit of numbers, and there seems to be no escape from the following general conclusions:

1. Two vols. of CNCl, representing the unit of numbers, the constituent weights, C=12, N=14, Cl=35.5, must each, likewise, represent the same number; the molecular weight is, therefore, contained in one vol. of N or Cl, but in two of CNCl and equal numbers are not contained in equal volumes.

2. The weights N=14, Cl=35.5 occupy in the free state one volume, but in the combination, CNCl, two volumes; their specific gravity is, therefore, by chemical action reduced to one half. The fact thus elicited of the variability and variation of the specific gravity is of fundamental importance and involves the irrelevancy of the mathematical demonstration of the hypothesis. In this demonstration the specific gravity is assumed to be constant, and this assumption not holding good, and the number of molecules in unit of volume being reduced to one half when the specific gravity is reduced to the same extent by chemical action, it is obvious that the mathematical proof must fail. Mr. Greene states that I have proceeded to demolish C. Clerk Maxwell's conclusion from mathematical reasoning. This is incorrect; I have found no fault with the conclusion of the celebrated mathematician, and consider his reasoning unimpeachable. I am also of opinion that he is entitled to great credit and respect for the prominent part he has taken in the development of the kinetic theory, and further think that it was for the chemists to produce the fact of the variability of the specific gravities, which they would probably not have failed to do but for the prevalence of Avogadro's hypothesis, which is virtually the assertion of the constancy of the specific gravities.

3. The unit of numbers being represented by Cl=35.5, it is likewise represented by H=1, and as the product of the union of the two elements is HCl, 36.5 = two vols., combination takes place by addition and not by substitution; consequently are

4. The elementary molecules not compounds of atoms? And the distinction between atoms and molecules is an artificial one, not justified by the natural facts.

5. Is the molecular weight not in every instance = two volumes?

These conclusions overthrow all the fundamental assumptions on which the hypothesis rests, and leave it, in the full meaning of the term, without support. Though Mr. Greene states that my arguments are based upon entirely erroneous premises, he has not even attempted to invalidate a single one of my premises.

As he considers the non-condensation to be natural in the case of cyanogen and chlorine, the condensation of two vols. of HCl + two vols. of H_3N to two vols. of NH_4Cl ought to appear to him unnatural. He, however, contends for it, and tries, on this solitary occasion, to strengthen his opinion by authority, though the proof, if it could be given, that ammonium chloride at the temperature of volatilization is decomposed into its two constituents, would be insufficient to uphold the theory.

The ground on which Mr. Greene assumes a partial decomposition at 350° C. is the slight excess of the observed density (14.43) over that corresponding to four vols. (13.375). There is, however, a similar slight excess in the case of the vapor of ammonium cyanide, the same values being respectively 11.4 and 11; and as this compound is volatile at 100° C and, at the same time, is capable to exist at a very high temperature, being formed by the union of carbon with ammonia, nobody has ever, as far as I am aware, maintained that it is completely or partially decomposed at volatilization. The excess of weight not being due, therefore, to such cause in this case, it cannot be due to it in the other.