■6o8 



NATURE 



[April 27, 1905 



points in the reasoning, however, and the proof consists 

 in showing- (i) that y satisfies the differential equation, 



(2) from the second formula that y = i — cos ( when x = o, 



(3) from the first formula that y and dy/di are both zero 

 when t = o, (4) from the first formula. that when t is finite 

 y is small for all large values of .v. If, now, x is finite 

 and t great, the second formula reduces lo y=— cos((+x), 

 so that the motion now consists entirely of waves pro- 

 ceeding tovaards the source of the disturbance — a most re- 

 markable result. If in the formula? for y we change the 

 sign of -v, the J functions are replaced by I functions. 

 The resulting value of y does not satisfy (4), and cannot 

 be accepted as a solution of the problem. 



H. C. POCKLINGTON. 



The Transposition of Zoological Names. 



Among the many radical changes in zoological nomen- 

 clature proposed of late years, none appear to me more 

 open to objection than those where names which have 

 long been in general use for particular species or groups 

 are transferred to others on the ground that they were 

 ■originally applied to the latter. One of the earliest of such 

 transpositions was suggested by Prof. Newton, of Cam- 

 bridge, who urged that Strix is not the proper generic 

 designation of the barn-owl, and that while this species 

 should be called A\uco flammeus, the tawny owl should 

 ■take the generic title Strix, as 5. ahico. I find, however, 

 that this emendation is not accepted in the British Museum 



Hand-list of Birds," where the barn-owl figures under its 

 familiar title of Strix flammea. Uniformity is not, there- 

 fore, attained by this proposal. 



Another instance occurs in the case of the walrus, which 

 was long known as Trichechus rosmarus, until systematists 

 •discovered that the generic title refers properly to the 

 manati, to which animal they transferred the name. 

 Again, the Simia satyrus of Linnaeus is now stated to be 

 the chimpanzi, and not the orang-utan, and consequently 

 Simia is made to stand for the latter instead of for the 

 former. As a fourth example of this transference of a 

 familiar generic name may be cited the case of the mar- 

 mosets of the genus Hapale, to which it is now proposed 

 to apply the title Chrysothrix, despite its practically 

 immemorial use as the designation of the titi monkeys. 



As an example of the transference of a species name, it 

 will suffice to take the case of the African antelope com- 

 monly known as the white oryx (Ory.-v leucoryx). This 

 name, it is stated, properly belongs to the Arabian Beatrix 

 oryx, to which it is accordingly proposed that it should be 

 transferred, after being so long used for the former animal. 



Personally, I am very strongly of opinion that such 

 transpositions should not on any account be permitted, and 

 that when a species or genus has been known bv a par- 

 ticular name for a period of, say, fifty years, this should, 

 ipso facto, give such an indefeasible title to that name 

 (altogether irrespective of its original application) as to 

 bar its transference to any other group or species. It 

 may, indeed, be deemed advisable that, as in the case of 

 the walrus, the old name should not be retained in the 

 generally accepted sense, but, if so, it should be altogether 

 discarded, and not transferred. The practice of trans- 

 ferring names must, if persisted in, inevitably lead to much 

 unnecessary confusion without the slightest compensating 

 advant.ige. Indeed, it will render such works as Darwin's 

 "Origin of Species" and Wallace's "Geographical Dis- 

 tribution of Animals," which are certain to live as bio- 

 logical classics, absolutely misleading to the next gener- 

 ation unless special explanatory glossaries are supplied. 



.Advanced systematists urge that those who refuse to 

 follow their lead in this and other kindred emendations in 

 nomenclature are not only old-fashioned and behind the 

 times, but that they are' absolutely doing their best to 

 hinder the progress of zoological science. This, however, 

 is but the opinion of a comparatively small fand, shall we 

 say, somewhat prejudiced?) section. What we really want 

 is the opinion of all those interested in zoologv and 

 natural history, namely, professional zoologists, palrconto- 

 logists, geologists, physiologists, anatomists, zoogeo- 

 graphers, amateur naturalists, and sportsmen. If the 

 general consensus of opinion of all these were on the side 

 NO. 1852, VOL. 71] 



of the proposed changes, and of others of a similar 

 type, then, and then only, 1 venture to think, could they 

 be regarded as obligatory. 



It may be added that the use of combinations, which 

 Mr. Stebbing has felicitously designated " comicalities in 

 nomenclature," of the type of Anscr anscr and usiiius 

 asiuns (or, still worse, Asinus asimis asinus, which is a 

 possible contingency), is rapidly tending to discredit the 

 common sense of scientific zoologists among matter-of-fact 

 men of the world. R. Lvdekker. 



A little known Property of the Gyroscope, 



To my surprise I have found that the property of the 

 gyroscope which I am about to describe, although perfectly 

 elementary, appears to be little known to either physicists 

 or astronomers. Neither is it mentioned in the text-books 

 so far as I am aware. That it has a very important bear- 

 ing on the mechanism of the solar system has been shown 

 in some of my earlier papers, but the laws which govern 

 the rotation and the simple facts themselves seem to be so 

 little understood that I have thought it worth while to 

 explain them more fully in this place. 



If a gyroscope is mounted on gimbals so that it may 

 shift its plane of rotation freely about an axis passing 

 through the plane of the revolving disc, we shall find it 

 is possessed of certain curious properties. To most persons 

 the notable characteristic of a gyroscope is the resistance 

 it offers to any force tending to change the plane of its 

 rotation. This is true of it only, however, in case certain 

 conditions are complied with. If these conditions are 

 neglected, it will change its plane with the greatest facility. 



If the wheel is properly balanced and mounted as above 

 described, and we set it spinning, it will continue to 

 rotate in one plane without change until it stops. Sup- 

 pose that while it is spinning we set it upon a table, and 

 cause the stand supporting it to revolve slowly about its 

 vertical axis. Instantly the wheel will adjust itself so as 

 to revolve in a plane parallel to the surface of the table. 



Furthermore, the direction of rotation of the wheel upon 

 its axis will be the same as the direction of rotation of 

 the stand. If we turn the stand in the opposite direction 

 the wheel will at once shift its plane, and turn over, so 

 as again to rotate in the same direction as the stand. 



.\nother way of showing the experiment is to hold the 

 stand supporting the gyroscope at arm's length. The 

 observer then slowly revolves upon his heels, first in one 

 direction and then in the other. Each time the observer 

 shifts his own direction of motion the gyroscope will shift 

 its plane, and always in such a manner that its direction 

 of rotation shall be parallel and in the same direction as 

 its revolution in its orbit. 



It is a well known fact that according to the nebular 

 hypothesis all the planets should have rotated in a direc- 

 tion opposite to that of their revolution in their orbits, just 

 as Neptune does at the present time. This is because by 

 Kepler's laws the inner edge of a revolving ring must 

 necessarilv move faster than the outer edge. The fact that 

 Neptune is the only planet that even approximately fulfils 

 this condition has always been a source of trouble to the 

 adherents of the nebular hypothesis. No one has ever 

 even attempted to explain the anomalous rotation of 

 Uranus, in a plane practically perpendicular to the plane 

 of its orbit. 



The interesting property of rotating bodies illustrated 

 above in the case of the gyroscope, and fully explained by 

 its theory, now at once makes the matter perfectly clear. 

 In the case of the planetary bodies, the force rotating the 

 sland of the gyroscope is supplied bv the annual tide raised 

 upon the planets by the sun. In former times, when the 

 planets were large diffuse bodies, this tidal force was of 

 considerable importance. Neptune, however, is so remote 

 from the sun that the tidal influence upon it has always 

 been small. The plane of its rotation, therefore, has been 

 but slightly shifted from that of its orbit — about •^^°. 

 Uranus being nearer the sun has had its plane shifted 

 nearly half-way over, or through 82°. The plane of rota- 

 tion of Saturn has been shifted through 153°. while that 

 of Jupiter has suffered a nearly complete reversal, and the 

 planet now revolves approximatclv in the plane of its 



