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NOTES AND NEWS.

THE recent publication is announced in Nature of the first number of a new monthly journal under the title Rivista di patologia vegetale. It is edited by Sigg. A. N. and A. Berlese, and published at Avellino, in Italy; and is to be devoted to the study of animal and vegetable parasites infesting cultivated plants, to the diseases which they cause, and the remedies employed to combat them.

- According to Nature, the Port Officer of Mangalore reports that a native craft was overtaken by heavy weather and made for Mangalore, where there is a bad bar with about eight feet of water on it. A tremendous sea was breaking over the bar, so, before crossing it, and while running in, the native skipper opened an oil cask, forming part of the cargo, and scattered it all round in the sea plentifully, with the result that he took his craft across the bar safely, and so saved the vessel and the cargo. The vessel's name was "Mahadeprasad," and she was of 95 tons, bound from Cochin to Bombay. This is said to be the first case on record of a native tindal who has successfully used oil in troubled

waters.

-In Science of July 8, the closing paragraph of the article by Dr. C. V. Riley, on "The Number of Broods of the Imported Elmleaf Beetle," should have read: "Our statement upon page 8 was a general one, based upon the observed shortness of the larval life, and upon the fact that the earliest larvæ mature before the end of May, and upon the additional fact that we know that newly developed beetles are found early in June. Prof. John B. Smith, in a paper read before the Entomological Club of the American Association for the Advancement of Science, in August of this year, made the statement that there is but one annual generation in New Jersey. The adult beetles develop from the larvæ which have fed during the summer, entering winter quarters as early as the first week in August. This state of affairs may probably hold in more northern regions, but in Washington it is safe to say that there are two generations, because, as just stated, newly developed beetles (the progeny of those which hibernate) appear in early June. These lay eggs, and, in fact, egg-laying may continue until the end of September, and larvæ have actually been found by Mr. Pergande in October."

- Mr. D. J. Macgowan, writing in the Shanghai Mercury, gives an account of some remarkable statements made by a group of Chinese traders who lately undertook a mercantile exploration of the interior of Southern Formosa. They started from Lamalan, which Mr. Macgowan takes to be Chockeday of the charts, and in seven days reached their objective point, Hualin Stream. They lodged in stone caverns, and the chattering of monkeys and the sounds of insects seemed to them "appalling and indescribable." The region was so "weird" that it reminded them of "legends of the kingdom of hobgoblins." Among the trees were some of "prodigious girth, forming a vast forest." These trees are said to measure more than ten outstretched arms. A tree said to flourish in the same forest is described as bearing "flowers, red and white, which are larger than a sieve, and of extraordinary fragrance." Mr. Macgowan adds: "Mr. Taylor, while searching for orchids, heard of these majestic trees and huge flowers, which he inferred, from what natives said, were epiphyte orchids. I am moved to make known this sylvan discovery in the hope that, pending the exploration of this terra incognita by our botanists, Dr. Henry or Mr. Ford, residents in Formosa will take measures to provide those naturalists with specimens of flowers, seeds, leaves, and bark of the trees concerning which the Chinese have excited our curiosity."

"The New Decimal Association, whose headquarters are at Botolph House, Eastcheap," says the London Daily Graphic of May 14, "has memorialized the Lords of the Committee of Council on Education on the desirability of taking an important step in connection with the introduction of the metric system in this country. The May examinations of the Science and Art Department are known through the length and breadth of the land, and much has been done by means of these examinations to popularize and extend technical study. The memorial which has been pre

sented recommends that in certain of the science examinations alternative questions be given in future, based on the metric sys. tem of measurement, which may be taken at the option of the candidate in lieu of questions based on feet and inches. In this way the large and intelligent class of candidates for certificates of the department will be induced to learn the metric system. The Committee of Council on Education has already ordered that the principles of this system should be taught in the higher standards of all elementary schools; and one of the steps taken by the school boards of London and other towns in consequence of this order has been to furnish the pupil teachers and advanced scholars with boxwood rules having a decimalized inch scale and a metric scale in juxtaposition. In addition to this, colored wall-charts of the metric weights and measures are used, and in this way the rising generation will to a great extent be prepared for the introduction of these weights and measures in future.

- The second annual geological expedition of the State University of Nebraska, undertaken by a party of six, left Lincoln for the field, June 21, 1892. This is known as the Morrill Geological Expedition, in honor of Charles H. Morrill, regent of the State University, whose liberality makes this work possible. The primary object of the expedition is the collection and preservation of geological specimens in general, but more particularly the palæontological forms for which the State and immediate surroundings are famous. The chief objective points are the Tertiary deposits of the White and Niobrara Rivers, and the Bad Lands of Nebraska, Wyoming, and South Dakota. The expedition is provided with tents, furnished by Governor Boyd, with teams and heavy covered wagons of the prairie-schooner type, and with apparatus, camping equipment, and provisions for the summer. The party consists of six members, exclusive of guide, - Mr. Thomas H. Marsland, Frederick C. Kenyon, Arthur C. Morrill, and Harry H. Everett, all of the State University of Nebraska, and James H. Haines of Iowa College, together with Erwin H. Barbour, acting State geologist, as professor in charge. The "Fossil Corkscrew, or Daimonelix, beds were visited first, and some tons of these extraordinary new fossils noticed and figured in Science, February, 1892 — were obtained. Native lumber and hay for packing are carried, and specimens are boxed as found, and delivered at the nearest station or siding. At the close of the expedition these scattered collections will be brought together and delivered at the State University in cars, which the railroad companies have generously offered for that purpose.

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-The eighth annual report of the Wisconsin Experiment Station devotes a large share of space to questions relative to ensilage. One chapter is devoted to a careful study, by F. H. King, of the construction and filling of silos. Mr. King, having visited 93 silos in Missouri, Michigan, Ohio, and Illinois, and several farmers while filling their silos, in order to obtain data for this chapter. Mr. King concludes that a stone silo, properly constructed, will keep the silage as well as a wooden one, but that it will be necessary to renew the cement lining frequently, or else to whitewash it with fresh cement every year, as the acids of the silage soon soften the cement. He finds that lath and plaster is a failure as a silo lining, both because of the softening of the plaster and the liability to injury with the fork in handling the silage. Of the wooden linings, that made by two thicknesses of boards with tarred paper between, all nailed firmly together, is showing greatest durability; but all wooden linings rot soon unless well ventilated. Painting the lining tends to hasten decay instead of preserving it. From an experiment in feeding corn silage in comparison with dry corn fodder, the following conclusions are reached: 1. A daily ration of four pounds of hay and seven pounds of grain feed, with corn silage or field-cured fodder corn ad libitum, fed to twenty cows during sixteen weeks, produced a total quantity of 19,813 pounds of milk during the silage period, and 19,801 pounds of milk during the fodder-corn period. 2. When we consider the areas of land from which the silage and fodder corn are obtained, we find that the silage would have produced 243 pounds more milk per acre than the dry fodder, or the equivalent of 12 pounds of butter. This is a gain of a little more than three per cent in favor of the silage.

SCIENCE:

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For Advertising Rates apply to HENRY F. TAYLOR, 13 Astor Place, New York.

A PLEA FOR A BROADER BOTANY.

BY L. H. BAILEY.

THE science of botany, as ordinarily considered and taught, has not laid hold of the full amount of territory to which it is entitled, and it has not, therefore, reached its full measure of usefulness. Strictly speaking, botany is the science of plants, but by general consent it appears to have dwarfed itself into a science of wild plants; or if it deals with cultivated plants they are such as fall to the care of botanical gardens, or, in other words, those which are cultivated for the sole purpose of maintaining a collection. It is not strange that in the earlier days botanists should have eliminated from their domain the whole realm of cultivated plants, for cultivation then meant little else than the maintenance and improvement of plants for merely economic purposes, and there was little science of cultivation. But now that the teachings of evolution have thrown a new purpose into the study of all natural objects, cultivated plants have acquired a fascinating interest from the abundant light which they throw upon variation and descent. In fact, aside from paleontology, there is no direction in which such abundant material can be found for the study of evolution as in cultivated plants, for in nearly all of them the variation is fully as great as in domesticated animals, while the species are very many times more numerous; and, by the fostering aid rendered by man, the accumulative effects of modified environment and selection are much more quickly seen and therefore more intelligible than in wild plants. My nearest neighbor, who is a paleontologist, and myself, a horticulturist, compare our respective fields of study to the decay and burning of a log. In both decay and burning the same amount of work is finally accomplished and the same amount of heat is evolved, but one process requires years, perhaps a century, for its accomplishment, and the other requires but a few hours. Cultivated plants afford within definite periods of time as much variation and progression as their wild prototypes exhibit in ages. So the garden is one of the best places in which to study evolution. It is a com

mon opinion, to be sure, that the variation of cultivated plants is anomalous and uninstructive because influenced by man, but this is wholly erroneous. I have yet to find a variation in cultivated plants which can not be explained by laws already announced and well known. It is strange that one can ever believe that any variation of natural objects is unnatural !

But wholly aside from the fascinations of pure science, cultivated plants and cultivation itself demand the attention of the botanists, for horticulture is nothing more than an application of the principles of botany. Just now, mycology is making important additions to horticultural practice, but there are greater fields for the applications of an exact science of plant physiology, whenever that science shall have reached a proportionate development. In short, the possi bilities in horticulture, both in science and practice, are just as great as they are in the science of botany upon which it rests; and inasmuch as it is absolutely impossible to separate horticulture and botany by any definition or any practical test, the two should go together in an ideal presentation of the science of plants. Horticulture belongs to botany rather than to agriculture.

men.

The ideal chair or department of botany, therefore, should comprise, in material equipment, laboratories, botanic garden. green-houses, orchards, vegetable and ornamental gardens, all of which should be maintained for purposes of active investigation rather than as mere collections; and I am sure that no department of botany can accomplish the results of which the science is capable until such breadth of equipment is secured. I am aware that there are difficulties in such a comprehensive field, but the only serious one is the lack of Botanists, as a rule, care little for gardens and cultivated plants, and horticulturists are too apt to undervalue the importance of scientific training and investigation; but the time cannot be far distant when men shall appear with sufficient scientific and practical training to appreciate the needs of the whole science and with enough executive ability Such men are no doubt to manage its many interests. teaching in some of our colleges to day, were the opportunity open to them. One cannot be a specialist in all or even several of the many subjects comprised in this ideal, but he may possess the genius to encourage and direct the work of other specialists. The first need is the opportunity, for there is not yet, so far as I know, an ideal chair of botany in existence, where the science can be actively studied in its fullest possibilities and then be presented to the student and the world.

Cornell University.

THE LAWS AND NATURE OF COHESION.

BY REGINALD A FESSENDEN.

DESIROUS of finding some relation between the conductivity of metals and their other physical properties, the writer, several years ago, began to tabulate all the data he could find. Realizing the uselessness of comparing the properties of substances whose natures are essentially different, as wood and iron, it was decided to confine the work to the elementary substances. It was found that the only elements whose properties were at all well known were those of the five chemical groups comprising the following metals: I., iron, nickel, cobalt, platinum, osmium, iridium; II, sodium, copper, silver, gold; III., magnesium, zinc, cadmium, mercury; IV., aluminium, thallium, indium, gallium; V., silıcon, tin, lead.

The data collected were not very concordant, but when they had been compared and the most probable values taken, laying due stress on the purity of the substances examined and the standing

of the observer, various regularities or laws were at once apparent, and it is for the purpose of pointing out one of these that the following paper has been written.

This piece of paper, taken as a whole, has certain properties, a certain size, a certain weight, a certain motion, and is the seat of a certain force which attracts other ponderable bodies to it. A single atom of matter has its weight, motion, size, and force. The weights of the atoms form the basis of electrometric chemistry, their motion that of the kinetic theory of heat. To their size less attention has been paid, we have only Mendelejeef's curve and certain experiments of Roberts-Austen, who has showed that the tensile strength of gold is weakened, not in proportion to the weight of the metal alloyed with it, but to the volume, in the same way as ten lumps of gravel weaken a casting more than ten grains of sand. Of the force the force of cohesion- still less is known, in fact absolutely nothing, and the object of this note is to point out what the nature of this force is and what its laws

are.

-

In its early youth science was riotously extravagant of ethers, and any puzzling phenomenon was considered warrant enough for the creation of a new one. As it has grown older it has grown also more economical, until at the present day the scientist who should ask for an appropriation of a new ether, to help him out of a difficulty, would be pounced upon. For this reason, if no other, we will confine ourselves to examining the various means by which our present ether has been supposed capable of producing the forces which cause cohesion.

1. Gravitation. There have not been wanting eminent scientists who have considered that gravitation could account for cohesion, and there have been many ingenious theories proposed, for instance that of Watts, who supposed that (since the effects of gravity on the moon's path may be supposed to consist of two parts, one independent of the shape of the earth and varying inversely as the square of the distance, the other dependent on the shape and varying inversely as the cube of the distance) if the atoms were of irregular shapes it might account for the effects. But no theory with gravitation as its basis will hold, first, because he effects are much too small; second, because, as we shall see, the cohesive force is totally independent of the weights of the atoms and depends on the size only.

2. Condensation and rarifaction of the ether caused by the motion of the atoms. If we hold a pith ball near a tuning fork the pita ball will be attracted up to a certain distance, and will then be repelled if brought closer. This theory has been a favorite with many, but, as such an attraction would vary with the motion of the atoms in a way that we know the force of cohesion does not, it also must be dismissed.

3. Electricity. That the force of cohesion was due to electricity has long been vaguely suspected. On the same principle apparently that electricity was considered to be the cause of life, i.e., "Life is a wonderful thing and unexplainable, electricity is a wonderful thing and unexplainable; therefore electricity is life" - the argument being possibly aided by an instinctive recollection of the Athenasion creed, which states that "there is only one incomprehensible." The writer is not aware that any evidence in favor of this theory was ever offered, so it was probably merely a guess.

Having rejected theories 1 and 2, we may see how the facts agree with the theory that cohesion is an electrostatic effect.

If we electrolyse a solution of silver nitrate, we know from Faraday's work that every atom of silver deposited on the electrodes carries over a certain quantity of electricity. This quantity is always the same, no matter how or when or where we perform the electrolysis, and this quantity seems to be related to the atoms in the same way as a pint of water to a pint measure. We may calculate the quantity on each atom in the following way. One cubic centimeter of silver weighs about 10.5 grammes One coulomb is carried over by every 1.12 milligrammes of silver deposited, therefore the charge on the atoms contained in one cubic 10500 centimeter of silver is 104 coulombs. 1.12

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The potential on each silver atom will therefore be about one volt. We may look at the cubic centimeter of silver as being made up of planes, each plane consisting of one layer of atoms. The distance between the centres of any two layers would be 10 8 centimeters. The potential on the atoms being one volt, the attraction between any two layers would be 4.5 X 10-11 X 13

-8

10 16

=

grammes per cm2 = 4500 kg. per cm2 = calculated tensile strength of silver 45 kg. per sq. mm. From Wertheim's results we have observed tensile strength of silver 38 kg. per sq. mm. That the calculated and observed results should be so close is of course only a piece of good fortune. We had no right to expect it, as the data upon which the calculation is based are not known with sufficient accuracy. Still, the result is a remarkable one, and places beyond question the fact that the known electric charges on the atoms can produce effects of the same order as those observed.

Having shown this, we may follow up the theory by investigating in what way the cohesion of the metals would vary if this were the case. Evidently (since every atom, large or small, has the same quantity of electricity, and the larger the atoms of a metal the farther away the centres of the atoms would be) the cohesive force should be inversely proportional to some power of

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As will be seen, the agreement is perfect, with the exception of iron, and those who are familiar how greatly the properties of iron are changed by the least particle of impurity will possibly agree with me in thinking that absolutely pure iron would be less rigid; in fact, some recent experiments show that it is so, being nearer 600 than 750; but I have not inserted this value, because a comparison with a set of observations made by one observer at one time and by one method would have a greater value than comparison with a lot of picked results from different observers. Assuming the electrostatic theory, we can easily calculate the exact function which rigidity should be of the atomic volume in the following way.

Suppose Figs. 1 and 2 to represent two cubic centimeters of different elements, of which the atoms of one are twice the diameter of the other, or, to put it more accurately, the distance between centres of atoms is twice as great in the one case as in the

other.

Let 1 contain the smaller atoms. Suppose one face made fast to the plank p, and both sheered slightly till they have the position shown by the dotted lines. It is evident that the ratio of work done in bringing the atom at G over to H to that done in bringing E to D, or C to A, will be the mean ratio of the force of attraction between K and G to that between E and F. This latter varies inversely as the square of the distance, according to the wellknown electrical law, and, consequently, as the distance G K is twice that of E F, the work done in moving E to D will be four times that done in moving G to H. Again, in Fig. 1 there will be 23 as many atoms to be displaced as in Fig. 2, so that, on the whole, there will be 22+ 23 as much work done in displacing the cube in Fig. 1 as in Fig. 2. In other words, the rigidity will vary inversely as the fifth power of the distance between the centres of the atoms, or as (atomic volume). Col. IV. gives the results calculated on this theory. As will be seen, they agree fairly well, as well as could be expected, considering the fact that we have left out one factor. This is the variation of rigidity with temperature, and as it would be obviously unfair to compare lead and silver at 600° C., it is obvious that our calculated results should only be applied when the metals are at some one point, say, at a temperature which is the temperature of their melting-point. As those metals having the greatest atomic volume, as a rule, melt at lowest temperature (though there are many exceptions to this) we may make a rough sort of formula, which shall give the rigidity at ordinary temperatures by multiplying again by the atomic radius, so we get (atomic volume) as the rate at which

FIG. 3.

2

FIG. 4.

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There is only one metal which does not agree with theory, and that is tin (iron, of course, on account of its impurities does not, but we know that, as we obtain iron more pure, we find its rigidity less, so there is very little doubt but that if it were absolutely pure the agreement would be closer). But it is easy to show that the observed results of tin are wrong. For the rigidity is given as 136 × 109 and the Young's modulus as 420 × 10o. There1 1 fore, if we represent Young's modulus by then 2 (a + b) Solving this we get b = .55 a. Therefore the bulk modulus

136 420

1

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is negative, and the more tin is compressed the larger 3 (a - 2b) it swells, a result which is absurd. This will emphasize the fact that the agreement between theory and experiment is as close as that between the experiments themselves.

Therefore, as

1

1

=

2 (a + b) 2.7

=

It will be noticed that the ratio-rigidity, Young's modulus, is 28 about Poisson's ratio for 78 these metals is, on the average, 0.35. Therefore the bulk modulus = 1.1 times Young's modulus, which agrees with the only datum I find in Everett, i.e., Wertheims's figures for brass, which gives the ratio 9.48: 10.2 1.08, very closely. All these moduli must contain the atomic volume to the same power, but this is not the case with the tensile strength; for, according to this electrostatic theory of cohesion, we may look at a wire as made up of thin discs, each disc consisting of a layer of atoms. The attrac tive force between any two such layers would vary inversely as the square of the distance between them and directly as the number of atoms in a layer. Combining these we find that it would vary as the fourth power of the atomic radius, or as (atomic vol

represent Young's modulus by, then the modulus of rigidity ume), making no allowance for the effect of temperature on the

1

1 is represented by and the bulk modulus by 2 (a + b) 3 (a-2b)' where b represents the lateral shortening accompanying the longitudinal lengthening a. So if b bears to a any constant ratio, then Young's modulus and the bulk modulus will each be some fraction of the modulus of rigidity. The continental writers, at least a b 1 good many of them, hold that Kelvin, Tait, and а Stokes say there is no relation. On the one hand, it is certain that

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follow that there is no relation between the two, and the evidence which has been brought to prove this has no value, for we have

I.

II.

III.

IV.

65

13.7

48

2,000 (?)

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complicated phenomenon than that of rigidity. Rigidity is simply a function of the cohesive force. The tensile strength of a substance depends not only on the cohesive force of the metal, but also on its ability to resist flow. If a metal did not flow before being pulled apart, there is no doubt but that its tensile strength would be proportional to the -power of the atomic volume. As, however, it does flow, and the amount of flow is not simply proportional to the diminishing of the cohesive force, we have to make a fresh allowance for it. In all the metals the melting-point is reached when the linear expansion has amounted to about 2 per cent. So when the cohesion has diminished about 4 per cent the atoms no longer hold the same relative positions, but one can slip in and take the place of another. So at equal distances from their melting-points only can the tensile strength be proportional to the power of the atomic volume. Consequently this ratio can only hold good with substances which have approximately the same melting-point. On examining the table, it will be seen that as copper, gold, and silver have approximately the same meltingpoint, the ratio does hold good with them. The same with tin and lead. Aluminium and zinc, which should be, the one slightly weaker, the other slightly stronger, than silver, have a melting-point about one-half that of gold and silver, and they have about half the strength at the temperature of comparison which they should have. The melting-point of iron and platinum is higher than that of gold or silver, and consequently their tensile strength is greater. The flow of a metal depends on two things, the cohesive force and the kinetic energy of the atoms. What function the flow is of the temperature, as reckoned in fractions of the temperature at which the substance melts, it is hardly worth while to go into now. If we suppose it directly proportional (though we may feel fairly certain it is not as simple a function) so that, at the same temperature, a metal melting at half the temperature that another does flows twice as easily, we get the following table, where Col. I. contains the observed tensile strengths, and Col. II. the calculated ones: -

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Col. III. gives the electrical resistance, silver being taken as 100, and it may be noticed that in any one group of metals the conductivity varies directly as the velocity of sound, and in passing from one group to another, by multiplying the conductivity by the valency we get proportionate values for all the metals. The same holds good for the heat conductivity. No close agree. ment can be expected here, for there are too many things to be taken into account. It is merely mentioned here because the fact of there being a relation between the velocity of sound and the conductivity for heat and electricity throws a light on the nature of these phenomena. This will form the subject of a separate paper. It may be asked how an electrostatic force can produce such effects. If the atoms are all similarly charged either + or they would repel each other and not attract. The explanation is probably this: The atoms, if we may call them so, of electricity are not infinitely smaller than the atoms of matter. When an atom is neutral it does not mean that it has no charge but that it has equal quantities of both kinds of electricity. The resultant effect of these charges on a body at a distance is zero, it behaves as if it had no charge, as shown below, in A.

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I have not been able to find any data on the tensile strength of magnesium. Theory gives about 9 kilograms for a wire 1 millimeter in diameter. It would be interesting to find if experiment confirms this.

If, when we have met with a new phenomenon in a substance, and are able to show that a certain property already known to exist in the substance is capable of producing effects of the magnitude observed, and that the phenomenon obeys the same laws as it would if it were caused by the already known physical property, we are to a certain extent justified in supposing that this property is really the cause of the phenomenon in question, and in applying our knowledge still further, we have seen that the charges which we know the atoms have on them are able to give effects of the same size as those observed in experiments on tensile strength, and that the various moduli follow the same laws as they would if cohesion were an electrostatic effect, and we may now apply our formula to other and less-known phenomena. The velocity of sound in a wire is given by the formula:

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If the atoms be brought close together there is a state of unstable equilibrium, and the effect is that either the charges move on the surface of the atoms or the atoms themselves move so that the atoms attract each other, as in B. Consequently all atoms

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