140 Proceedings of the Royal Physical Society, 



term " spheroidal." All fluids became spheroidal when re- 

 leased from the cohesive attraction of surrounding solids or 

 fluids, and their release was due in every case to the inter- 

 position of a thin plate of air or vapour between the " sphe- 

 roidal" globule and the substance over which it floated. It 

 was a mistake to suppose that " repulsion" took place in 

 these cases. The term " repulsion" had no meaning in 

 physical science. The author then exhibited to the Society 

 the production of the " spheroidal" state in fluids by various 

 mechanical and electrical contrivances, and explained the 

 mode of action of the latter. He then repeated the experi- 

 ments of Boutigny by the aid of large and accurately ad- 

 justed plates of heated copper, on which globules and plates 

 of various fluids rolled and floated without actual contact 

 with the metal, and were, thrown into various undulatory 

 and symmetrical figures, such as crosses, transparent domes, 

 toothed wheels, &c, by the intermittent action of com- 

 pressed vapour, while forming and escaping from their lower 

 surfaces. At a late meeting of the Society Dr Macadam 

 had advanced, that the outer shell of the earth was main- 

 tained at a considerable distance from its incandescent 

 nucleus by the existence of the " spheroidal condition" on 

 the inner surface of the former. Dr Wright dissented from 

 Dr Macadam's theory, inasmuch as it was impossible that 

 the shell and nucleus could be maintained at other than an 

 exceedingly minute distance by the hitherto observed laws 

 of spheroidal action ; that matter, when maintained in the 

 spheroidal state by heat, was subject to incessant motion 

 and waste from evaporation, which w T ould not only prevent 

 the formation of a continuous shell, but would break up or 

 distort that shell, if momentarily formed, by pressure from 

 within : and that the observed shape of the earth was that 

 which a mass of homogeneous inelastic fluid would take 

 during rotation ; while a compound mass (such as a fluid 

 shell surrounding a fluid nucleus, and separated from it by 

 a layer of elastic aeriform fluid) would either break up into 

 a ring on rotation, or exhibit a bulging at its weakest parts 

 — the poles. This actual agreement between the observed 

 shape of the earth and its calculated shape as a homogeneous 



