TRANSACTIONS OF SECTION A. 249 



about the space now occupied by the atom is a consequence of tbe presence of 

 the atom, it is in no way owing to its action on tbe etbereal medium. 



Tbe author then argues that if every material atom, so must every compound 

 system of atoms, i.e., every material body, whether gaseous, liquid, or solid, have 

 an ethersphere, which not only surrounds the whole body, but also penetrates the 

 interstitial spaces of the body which lie between its atoms. 



By means of these etherspheres the author believes the phenomena of heat 

 may be satisfactorily accounted for, on the supposition that the ethereal medium is 

 the medium of heat as well as of light. They are shown in the original memoir 

 itself to have a remarkable bearing also on the phenomena of magnetism, electricity, 

 galvanism, and the various sciences connected with the agency of imponderables. 

 He therefore concludes that etherspheres constitute a vera causa the existence of 

 which in nature is as certain as is that of the ethereal medium itself, about which 

 no philosopher expresses doubt in the present day. 



4. On some New Instruments recently constructed for the continuation of 

 researches on Specific Inductive Capacity. By J. E. H. Gordon, B.A., 

 Assistant Secretary of the British Association. 



Mr. Gordon exhibited and explained the following new instruments which he 

 has arranged during the last year : — 



(1) A minature five-plate induction balance, similar in principle to the large- 

 balance exhibited at the Dublin meeting, but intended for the examination of crystals 

 and other precious substances which cannot be obtained in sufficiently large quan- 

 tities for the large balance. 



The large balance requires the dielectric plates to be 7 inches square and £ to 

 f inch thick. For the small balance it is sufficient to make them 2 inches square 

 and £ inch thick. 



(2) A gauge for measuring the thickness of the dielectric plates to 10 q 00 inch. 



(3) A new form of quadrant electrometer for use with the small induction 

 balance. 



The capacity of the smaller plates of the little induction balance is so minute 

 that when they are attached to the quadrants of the electrometer of ordinary con- 

 struction (Elliott pattern) disturbances in them produce hardly any effect on the 

 needle, on account of the much greater capacity of the quadrants of the electrometer. 



In order to construct an electrometer whose quadrants should have very small 

 capacity, and which should yet be very sensitive, the author has arranged the 

 quadrants as pieces of a flat disc, only one inch in diameter, and tbe needle has been 

 bent round them so as to be acted on by both their upper and lower surfaces and 

 their outside edge. 



(4) A new rapid commutator. 



This was invented by Professor Cornu, of the Ecole Polytechnique, Paris, who 

 had the great kindness to devise it for the author of this paper, who, when M. 

 Cornu took up the matter, had just constructed three different instruments for the 

 experiments for which this one is intended, all of which had proved unsuccessful. 



Some preliminary experiments with M. Oornu's instrument have shown that it 

 promises to be entirely satisfactory. It can be used with either the large or small 

 induction balance on the one hand, and with a Holtz machine or battery of 500 or 

 more cells on the other. It reverses the electrification of the plates of the balance 

 eighteen times per second, and between each reversal, short circuits, and puts 

 to earth both poles of the induction balance and both poles of the battery. By 

 altering two screws it can be arranged to short circuit and put to earth the poles 

 of the induction balance only, and to insulate the battery poles. 



(5) Driving-wheel for the Cornu commutator. 



All the instruments have been constructed by Mr. Kieser of the firm of 

 Elliott Brothers. 



