500 Intelligence and Miscellaneoics Articles. 



in nature^ which is modijied by the accidental and varied conditions 

 to which it is subjected^ hut that its essential nature and characteristics 

 are at all times unchangeably tha same. 



CAMBRIDGE PHILOSOPHICAL SOCIETY. 

 [Continued from p. 421.] 



May 6, 1851. — Of the Transformation of Hypotheses in the 

 History of Science. By W. Whewell, D.D. 



The author remarks that new theories supersede old ones, not 

 only by the succession of generations of men, but also by transfor- 

 mations which the previous theories undergo. Thus the Cartesian 

 hypothesis of vortices was modified so that it explained, or was sup- 

 posed to explain, a central force : and then, the Cartesian philoso- 

 phers tried to accommodate this explanation of a central force to the 

 phaenomena which the Newtonian principles explained ; so that in 

 the end, their theory professed to do all that the Newtonian one did. 

 The machinery of vortices was, however, a bad contrivance to pro- 

 duce a central force ; and when it was ai)plied to a globe, its defect 

 became glaring. Still however, the doctrine of vortices has in it 

 nothing which is absurd anterior to observation. The " nebular 

 hypothesis" is a hypothesis of vortices with regard to the origin of 

 the system of the universe, and is now held by eminent philosophers. 

 Nor is the doctrine of the universal gravitation of matter at all in- 

 consistent with some mechanical explanation of such a property ; 

 for instance, Le Sage's. We cannot say therefore that if the planets 

 are moved by gravitation, they are not moved by vortices. The Carte- 

 sians held that they were moved by both : by the one, because by 

 the other. 



Like remarks may be made with respect to the theories of mag- 

 netism and of light. 



LXXV. Injtelligence and Miscellaneous Articles. 



ON THE CONSTITUTION OF THE ATMOSPHERE. BY M. LEWY. 



npHE memoir which I have the honour to submit to the Academy 

 -■- contains the results of a series of researches on the constitu- 

 tion of the atmosphere, executed between France and New Granada, 

 and from the coast up to 3193 metres above the level of the sea. 



The analyses were performed by the new process of MM. Reg- 

 nault and Reiset, which consists, as is w^U known, in analysing the 

 air by volumes. To measure the elastic forces of the gas, I em- 

 ployed an excellent cathetometer constructed by M. Perraux ; the 

 process thus combined enables us to obtain much greater precision 

 than has hitherto been reached in this class of experiments. To 

 judge of the degree of accuracy attainable, it suffices to examine 

 the numerical details of two analyses ; and it will be seen that the 

 greatest difference between two analyses made with the same sample 



