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TRANSACTIONS OF THE SECTIONS. 91 
bodies. A wax model of calcareous spar was exhibited by Dr. Tyndall, the deport- 
ment of which, as proved experimentally before the Section, was precisely the same 
as that of a calc-spar crystal of the same size and shape. Similar experiments were 
made with other substances, both magnetic and diamagnetic, and all went to esta- 
blish the result—a result assented to by Prof. Thomson, who witnessed the experi- 
ments—that the phenomena in question are not due to the shape of the molecules, 
but ¢o their manner of arrangement. 
AstTRoNoMy, METEORS, WAVES. 
On the connexion between Geological Theories and the Theory of the Figure 
of the Earth. By Henry Hennessy, WRLA. 
As geology may be considered to embrace an examination of the form and struc- 
ture of the earth, it follows that every correct geological theory must be capable of 
explaining the greater as well as the lesser inequalities in the figure of our planet. 
Certain geological theories being incompatible with the supposition that the earth 
was originally in a state of fluidity, attempts have been made to account for its 
spheroidal figure by the abrading action of the waters at its surface. It has been 
shown by Playfair and Sir John Herschel that the earth wou!d from such causes 
ultimately tend to assume the form of an oblate spheroid ; but neither of these emi- 
nent mathematicians have presented such numerical results as would enable us to 
compare the theory with observation satisfactorily. This the author has effected in 
a paper communicated to the Royal Irish Academy, in which he deduces for the polar 
compression, according to the theory in question, 3. The compression given by 
measurements is 335 ; consequently it seems that the theory of the earth’s primitive 
solidity must be rejected in favour of that of its primitive fluidity, which perfectly 
agrees with observation. 
The author also pointed out an inconsistency between the theory of the earth’s 
primitive solidity and the theory of climates proposed by Sir Charles Lyell in order 
to account for the diminution of temperature at the earth’s surface since early 
geological epochs. This theory would require a gradual transport of matter from 
the equator to the poles in order to account for a diminution of the heating surface 
of dry land at the equator. Consequently on this theory the earth would tend to 
become prolate instead of oblate. The author concluded by pointing out similar 
objections to the geological views known as the Neptunian theory and the chemical 
_ theory of volcanos. 

Proposed Theory of the Origin of the Asteroids. 
By James Nasmytu, F.R.A.S. 
As the progress of science is frequently aided by advancing hypothetical views in 
explanation of the cause of certain phenomena, Mr. Nasmyth desires to hazard a 
suggestion as to the cause of the break-up of the original planet whose fragments, it 
has been conjectured, form that numerous and remarkable group of small planets 
revolving between the orbits of Mars and Jupiter, some peculiarities of whose path 
have led to the supposition that they must have parted company from a parent mass 
at the same time and place. In order to render his views on this subject more clear, 
he would refer to the well-known toy called a ‘‘ Prince Rupert Drop,” namely, a drop 
of glass which has been let fall while in a semifluid state into water, by which the 
surface of the glass-drop is caused to cool and consolidate with such rapidity that 
the subsequent consolidation and contraction of the interior mass induces so high 
a degree of tension between it and the exterior crust that the slightest vibration is 
sufficient to overcome the cohesion of the external crust, and by so letting free the 
state of tension cause the glass-drop to fly into thousands of fragments. Nor is 
