December 22, 1893.] 



SCIENeE 



Mi 



If the solid is melted it is called a fluid, and is com- 

 monly sujjposed to be unable to withstand a shearing 

 stress. This is due to the following circumstance: Let 

 us press down A. If B did not move, then B would have 

 to follow A, if it were not that in a fluid the atoms no 

 longer oscillate about a fixed point, but change their posi- 

 tions relatively to one another. The atom B moves at 

 ordinary temperatures at a velocity of somewhere near 

 100,000 centimetres per second. The distance be- 

 tween any two atoms is somewhere in the neighbor- 

 hood of l/100,000,000th of a cm. Consequently in the 

 1/1, 000,000,000,000,000th of a second, the atom B will have 

 passed without the radius of attraction of A. Conse- 

 quently we see that for any forces which are impressed in 

 a greater time than 10~'' second, the fluid will have no 

 rigidity. But if the force is applied in less time, we have 

 no reason for supposing that the fluid will not resist 

 shearing, or that a water tuning fork could not be con- 

 structed at the centre of the earth. For, if we accept the 

 electrostatic theory of cohesioQ, the force which A exerts 

 on B when A is pulled down travels at the rate of more 

 than 10" c. m. pier second. As B will have to move say 

 10^" c. m. to get out of the way of the jjull from A, we see 

 that if an impulse is given in less than 10~''"th of a second, 

 B will be j^ulled down, and the fluid will resist a shear. 

 And it is this force which acts to join the atoms together 

 which gives rise to the phenomenon of surface tension. 

 Consequently we see that if the ether has rigidity, 

 whether it be a solid or a fluid, it must have surface ten- 

 sion. 



Let us take the case of two bubbles of air in water. 

 There is a surface tension at the junction of the air and 

 water, and it may be shown that the effect of this is to 

 bring the two bubbles together. A similar result would 

 follow if the two bubbles had their places taken by two 

 drop)s of water hotter than the rest of the. water. Or if 

 the dropis were made ujJ of a nvimber of concentric shells, 

 the density of each shell being greater than that of 

 the shell next inside it, the equivalent of such a 

 shell would be produced by sticking the prongs of 

 two tuning forks into the water, for at those places 

 where the velocity of a jjrong was greatest the density of 

 the water in unit volume would be least, and the forks 

 would be attracted. So if we suppose the atom to be, 

 aaj, a Thomson vortex ring, and that this vortex ring, in 

 virtue of its rotation, renders the ether next it less dense, 

 or less rigid, it would attract any other atom similarly 

 constituted in the same manner as we know two atoms 

 do. And this attraction would be always the same in 

 quantity, no matter what the temperature or surround- 

 ings, so long as the atom was the same, i. e., its weight 

 would be constant. And if another atom produced a dif- 

 ferent degree of density or rigidity near it, its weight 

 would be different and constant. 



Thus we see that if the ether has inertia (or some 

 "counter motive force"' opposes its motion), then matter 

 must have inertia, and if the ether has rigidity, and atoms 

 produce a dift'erence in the cohesion of the ether near 

 them, th-en all atoms will attract each other in proportion 

 to the change they produce in the rigidity of the ether 

 near them. 



There are two experiments which seem at first sight to 

 contradict Fizeau's experiment. First, the fact that a 

 rotating disc of matter has no effect on a magnetic needle 

 placed at its centi-e. Second, the fact that light suffers 

 no retardation or acceleration when passed along the 

 lines of force between two plates at different potentials, 

 and placed in an electrolytic bath. 



The first is readily explained when we consider that 

 when the disc is rotating it is carrying with it ether as a 

 whole, i. e., equal quantities of positive and negative elec- 



tricities, or is equivalent to two currents of equal strength 

 flowing in opposite directions, and consequently can pro- 

 duce no effect outside of the body. Or, to use Prof. J. J. 

 Thomson's symbolism, the ends of the Faraday lines are 

 both within the body, and do not pass outside, whereas 

 in Professor Rowland's experiment the Faraday lines 

 have one terminal on the disc, and the other outside. The 

 two cases are not similar. 



The second case, that of the electrolytic bath. In this 

 the ether does not move as a whole, there is merely a 

 shearing of plus and minus electricities past each other, 

 and the algebraic sum of the velocities of the components 

 of the ether is therefore zero. Or, the ether does not 

 move, so far as any possible effect on light is concerned. 



THE "GLACIAL PERIOD" PROVED AS A NECES- 

 SARY CONSEQUENCE OF THE EARTH'S MOVE- 

 MENTS. 



BY MA-JOR GENERAL J. C. COWELL, WINDSOR CASTLE, ENGLAND^ 



From the increasing interest that is manifested in 

 all that relates to the glacial period, and the discov- 

 ery, by General Drayson, of the Second Rotation of 

 the Earth, it will be of value to those who are study- 

 ing the geological evidences of the ice ages, to devote 

 some time to the ascertained facts proving the Second 

 Rotation as compared with the accepted theories, since 

 these appear to sujaply all the conditions necessary for 

 the explanation of the glacial phenomena, at regular 

 intervals; and it is with the object of rendering the sub- 

 ject clear to them that the following remarks are offered 

 to the readers of Science. 



It has hitherto been stated by Herschel and other 

 writers of his day, that the movement of the Earth, which 

 caused the precession of the equinoxes and solstices, and 

 the changes in Polar distance, and Right Ascension of the 

 Stai-s, is "a conical movement of the Earth's axis round 

 the pole of the Pole of the Ecliptic as a centre." 



Drayson claims that this definition is vague, if not mis- 

 leading, even as regards that part which spieaks of a con- 

 ical movement of the axis. He claims that it is the two 

 half axes that trace cones, the apex of these cones being 

 at the centre of gravity of the Earth. 



He also claims that this conical movement of the two 

 half axes is the mere mechanical result of a Second Rota- 

 tion of the Earth, just as the conical motion every twenty- 

 four hours, of all lines from the Earth's centre to points 

 at the Earth's surface, is the result of the daily rotation 

 of the Earth. 



An examination of the annual changes in Right Ascen- 

 sion of every Star in the Heavens (see pages 163 to 219 

 in "Untrodden Ground in Astronomy and Geology") 

 proves that a second rotation is the only movement which 

 will explain the recorded changes in the Right Ascension 

 of Stars. Hence, instead of some vague and undefined 

 movement of the Earth occurring whilst the axis has 

 what has been called "a conical motion," the detail 

 movements of each point on the Earth's surface are accu- 

 rately defined by the second rotation. Secondly, the 

 Earth's axis traces a circle round the Pole of the Ecliptic 

 as a centre, keeping constantly at the same distance of 23^^ 

 28' from it, wrote Herschel and others. 



In the face of the fact that the obliquity (i. e., the 

 angular distance between these poles) decreases about 

 ■17 " per century, the above statement is obviously erron- 

 eous. 



As an escape from this error it has been asserted by 

 some that the Pole of the Heavens moves about 20" 

 annually at right angles to the arc joining the Pole of the 

 Heavens with the Pole of the Ecliptic, but as the latter 



