Vol. XXn. No. 10.] 



POPULAR SCIENCE NEWS. 



147 



or rush family. The flowers are borne on slender 

 spikes, often three or four feet long, starting from 

 among the crown of leaves at the summit of the 

 stem. The species are often known in Australia 

 as black-boy trees, in consequence of the fancied 

 resemblance of the trunk and flower-spike at a 

 distance to a native holding a spear. 



Down the centre of the room are glazed stands 

 containing a series illustrating the manufacture of 

 articles of wood such as that of violins at >[unich, 

 and of children's toys for Noah's arks, as carried on 

 in Saxony. For these the rough design of the ani- 

 mal required for representation is first turned in a 

 circular piece of wood by the lathe; sections are 

 then cut out, and very little handwork produces from 

 the same circle a sheep or a wolf, a horse or an 

 elephant. 



On the ceiling is a representation of Amorpho- 

 phallus tilanum (Becc), a gigantic ai'oid, native of 

 Sumatra, whose three-parted, compound leaf rises 

 to the altitude of a tree, while the blossom, a bur- 

 den for two men to carry, rises from the root with 

 spathe and spadix, after the fashion of our Indian 

 turnip. 



But one does not go to Kew for study only, and 

 some time must be given to the mere enjoyment 

 of the beauties of tropical and temperate vegeta- 

 tion as offered in the palm-house, conservatories, 

 and various houses for tree-ferns and water-lilies, 

 and in the Gardens themselves and the extensive 

 arboretum. Here old trees spread their branches 

 with a luxuriance that speaks of a century of care- 

 ful guarding, and avenues and vistas of young 

 ones promise a continuation of beauty for the 

 future. Pines, spruces, firs, and yews, the cedar 

 of Lebanon, the deodara of India, and California 

 sequoias, all thrive at Kew as heartily ai native 

 trees, and in their own natural beauty, and the 

 added beauty of their surroundings, form pictures 

 never to be forgotten. The Royal Botanic Gar- 

 dens at Kew are indeed a paradise to the lover of 

 nature, and fain would he linger indefinitely 

 among their treasures. 



[Original in Popular Science News.] 



THE TENDENCY OF MATTER AT THE 

 SURFACE OF THE EARTH. 



BY W. A. ASHE, F.R.A.S. 

 I'AKT I. 



It is a very popular belief , and one that is taught 

 in all elementary text-books bearing on the subject, 

 that matter at the surface of the earth has a ten- 

 dency towards the poles; because, as it is said, of 

 the greater value of gravity there. That this be- 

 lief is held.by others than the unscientific, the follow- 

 ing quotation from Mr. Proctor's " Saturn and his 

 System" will sufficiently prove; and it will serve to 

 point out how general and unquestioned this belief 

 is as well. He says, " It appears probable that 

 fluid masses at the surface of such a planet would 

 tend to form two vast polar oceans, since gravity is 

 so much greater at Saturn's poles than equator." 



Mr. Proctor is, of course, speaking of the ten- 

 dency of matter at Saturn's surface; but the con- 

 clusion is equally applicable to the case of any 

 heavenly body having a motion of rotation and, 

 presumably, compression, as pointed out in the 

 first part of the quotation used. It is evident that 

 this tendency is attributed to the fact of Saturn's 

 polar being less than its equatorial diameter, al- 

 though the statement is made as if the effect were 

 produced by reason of the single fact of gravity 

 being greater at the poles than equator, — a char- 

 acteristic that belongs to every rotating sphere, 

 and which we know, at least in the first place, does 

 not produce a poleward tendency; for it is by 

 means of this motion of rotation that a sphere is 



transformed into a spheroid, by tlietransferrence of 

 its particles, under the influence of gravity and the 

 centrifugal force that has by this means been gen- 

 erated, from about the poles towards'the equator; 

 so that we are justified in assuming that the mere 

 fact of gravity being greater at the poles than 

 equator is insufficient of itself to produce a ten- 

 dency in this direction. There are other circum- 

 stances, as we shall presently see, that require to 

 be considered before we can predict the direction 

 of the tendency of matter at the surface of any 

 rotating solid. 



It may aid towards the general understanding of 

 the fallacy contained in this very popular belief and 

 Mr. Proctor's statement, to express his conclu.sion 

 in the following way: " If a sphere is caused to 

 rotate about an axis, we know that an oblate sphe- 

 roid will be developed if the particles forming its 

 mass are free to move; if not, that there must be 

 a tendency in the direction of that solid, as the 

 result of the forces now acting upon it; but once 

 this solid has been developed, or partially devel- 

 oped, should viscosity or any other cause prevent 

 its being fully so (the possibility of the sjJieroid 

 being over-developed not being at present consid- 

 ered), then the particles of its matter will move, or 

 have a tendency to move, back to the outline of 

 the perfect sphere, in opposition to the still exist- 

 ing forces that they moved in response to in ac- 

 quiring their present position." 



If we consider such a section of the sphere and 

 spheroid as would be represented by the circle and 

 ellipse, it would seem evident that any fluid mass 

 on the latter must have a tendency to move towards 

 the poles or minor axis, because of the very evident 

 " down-hill " course it would be following in 

 moving in this direction; but it is just on what 

 we mean by the term " down hill " that every thing 

 depends. If, in the sphere or spheroid, we con- 

 sider that direction as downwards which approaches 

 nearer the centre of gravity than the other, then, 

 certainly, would matter have a tendency towards the 

 poles in the case of the earth or any other similar 

 figure. This is a correct definition of the term 

 " downwards " in every case that we may consider, 

 in which the body is a.ssumed as being at rest; 

 but, once a motion of rotation is given to it, our 

 horizontal plane, or plane of reference, is so altered 

 in position, that what may have been downwards 

 in one case need not be so in the other. As an il- 

 lustration, let us consider the case of a sphere at 

 rest, covered with a film of water. In this case 

 we know that there will be uniform distribution of 

 the film over the whole surface, chiefly because the 

 action of gravity is everywhere at right angles to 

 the surface of the sphere about which the waters 

 are distributed, or to the hoiizontal plane. Now, 

 if our sphere acquires a motion of rotation, a new 

 force is brought into existence (the centrifugal 

 force), which, acting in a direction different to 

 that of gravity (except at the poles and equator), 

 produces a resulting tendency to movement in 

 matter, which is in every case different to that it 

 would have had, had it been acted upon by the 

 force of gravity alone. The angular difference be- 

 tween the direction in which gravity alone would 

 have acted, and that in which the combined in- 

 fluences of gravity and the centrifugal force are 

 acting, is called the " angle of the vertical; " the 

 plane at right angles to this combined influence, at 

 every point of the surface of our solid, the " hori- 

 zontal plane; " and, onlyby knowing the difference 

 between this and the actual surface of the solid we 

 are considering, is it possible to state what direc- 

 tion on the mean surface of our solid is to be con- 

 sidered " downwards." Thus, it will be seen, 

 that, to predict the direction of the tendency of 

 matter at the surface of any rotating solid, we 



must consider, in connection with the visible out 

 line it presents, what the resulting direction of the 

 combined action of gravity and the centrifugal 

 force is with reference to the surface; and, as this 

 resulting direction depends entirely on the value of 

 the centrifugal force (which is itself dependent on 

 the rate with which the solid is rotating, or its 

 diurnal motion), it is essential that in considering 

 the resulting tendency of matter at the surface of 

 any solid, we should remember that all such con- 

 siderations as to whether gravity is ever other than 

 greatest at the poles, or whether the polar or equa- 

 torial diameters are the greater, are insufficient of 

 themselves for the determination of the question 

 proposed. Invariably, no matter what the appar- 

 ently exaggerated outline of the solid we are con- 

 sidering, if that outline is the natural development 

 of one solid into another, the existing condition 

 must be more nearly one in which the particles of 

 its matter are at rest, than was that of the first; 

 and, failing their having reached the solid of equi- 

 librium corresponding to the existing forces, owing 

 to their motion having been arrested whilst pro- 

 ceeding in the required direction, then their ten- 

 dency must be in the direction of that original 

 motion, or towards the equator; so that, were 

 their ability to move increased, this would be the 

 direction of their movement. 



(Concluded next month.) 



[Special correspondence of the Popular Science Newn.] 

 PARIS LETTER. 



The principal scientific event of late is the meet- 

 ing which has been held of the Congrfes pour 

 I'fitude de la Tuberculose in Paris. The initiator of 

 the project was Professor Verneuil, and the meet- 

 ing was presided over by Professor Chauveau, the 

 well-known physiologist. The second meeting is to 

 be held two years hence under M. Villemin's presi- 

 dency. M. Villemin is the pioneer of the recent 

 notion of contagiousness and of the infectious 

 nature of tuberculosis, and his pait in the advance 

 of science has been a very great one. 



Many interesting papers have been read, but 

 none of any very great importance, — none that are 

 epoch-making at all. M. Nocard, of the Paris 

 Veterinary School, gave some useful information 

 concerning the danger of the milk and meat of 

 tuberculous animals to the health. Although the 

 milk of a tuberculous cow contains tuberculous 

 bacilli only in the case of local mammary tuber- 

 culosis, the Comitedes Epizootrcs has forbidden the 

 sale of the milk of such cows, and allows it to be 

 used in situ and for animals only, after boiling. 

 Generally speaking, M. Nocard says, that, as it is 

 impossible practically in a large town to ascertain 

 the exact origin of the milk sold in it, the milk, 

 especially for children's use, should always be 

 boiled. If unboiled milk were absolutely neces- 

 sary, one should use goat's milk, as tuberculosis is 

 extremely rare in this sort of animal. Concern- 

 ing the flesh of tuberculous animals, Bouley was 

 of the opinion that it should be entirely prohibited; 

 and his motion carried the day in a meeting held 

 in Antwerp. But the strict regulations prescribed 

 by this meeting were never enforced ; in fact, they 

 were much too strict. Numerous experiments have 

 shown, before and since, that a tuberculous animal 

 is not tuberculous in all its parts, and that the flesh 

 is very rarely so, even when the lungs or viscera 

 are extremely tuberculous. So, in 1885 it was 

 resolved in France to prohibit the sale of the flesh 

 of tuberculous animals only when the tuberculous 

 bacilli are found out of the affected organs or of 

 the corresponding lymphatic ganglia. 



When the bacilli are found only in these parts, 

 the flesh is allowed to be sold ; the diseased organs 



