210 Prof. F. Guthrie on the Axial Rotation of the Earth, 



near the borders of the continent or hollow, and also at the anti- 

 podes. In such an irregular system as our globe actually is, 

 these causes of disturbance are, no doubt, to a great extent anta- 

 gonistic one to another; and he must have a wonderful sagacity, 

 or be very rash, who should attempt to conjecture the total 

 effect, at any place, of the existing configuration of land and sea. 

 Still the fact remains, that the surface of the sea cannot be 

 regular, and that the irregularities must shift and vary as the 

 disposition of the land changes. 



Kitlands, Dorking. 



XXXII. A Speculation concerning the relation between the Axial 

 Rotation of the Earth, and the Resistance, Elasticity, and Weight 

 of Solar JEther. By Professor Frederick Guthrie*. 



THE line of argument in the following paragraphs is 

 this :— 



If solar aether resists the translation of matter, and if solar 

 space be filled with aether of uniform resisting power, then the 

 effect of such an aether would be to tend to cause the earth to 

 revolve on its axis in a direction opposite to that in which it 

 actually revolves. 



But if the aether has weight and elasticity, and if its resist- 

 ance increases with its density, then solar aether might convert 

 a portion of the orbital. motion of the earth into axial rotation in 

 the direction in which it actually revolves. 



And hence it is not impossible that the axial rotation of the 

 earth may be due to the conversion of a part of its orbital motion 

 by the resistance of the solar aether, the solar aether having 

 weight. 



1. Gravitation explains both the translation of the earth and 

 its retention in a circumsolar orbit. But the daily or axial rota- 

 tion of the earth cannot be referred to the same force. 



2. When a body moves in any path without rotation, that is, 

 in such a manner that any fixed line in it retains its original 

 direction, or any two positions of the same line are parallel to 

 one another, then every point of the body traverses a path of 

 the same, length and shape. 



3. If a circle moves without axial rotation in a circular orbit, 

 all points on or in the circle describe circular orbits whose radii 

 are all equal to the distance between the centre of the moving 

 circle and the centre of the orbit. 



4. If, on the moving circle, a point, which at starting is at a 

 certain distance from the centre of the orbit, moves uniformly 



* Communicated by the Author. 



