568 Intelligence and Miscellaneous Articles, 



5. The total mechanical force exerted by a volume of air while 

 expanding indefinitely is proportional to its G temperature. 



6. A given quantity of air while expanding, under a constant 

 pressure, from one temperature to another, exerts a mechanical force 

 equivalent to one-third the diiference of temperature ; and the quan- 

 tity of heat required to change the temperature of air under a con- 

 stant pressure, is four- thirds of that required to effect the same change 

 of temperature with a constant volume. 



The author concludes by observing that it is singular that these 

 simple and, he considers, important deductions from MM.Gay-Lussac 

 and Welter's experiments, have been overlooked by the eminent ma- 

 thematicians who have elaborately discussed this subject. The arti- 

 ficial position of the zero-point on the ordinary scales of temperature 

 may perhaps account for this by its tendency to confine our ideas. 

 Dalton's and Gay-Lussac*s law of expansion seems imperatively to 

 have required that, in all computations having reference to gases and 

 vapours, the temperature should have been reckoned from the zero 

 of gaseous tension ; yet it has not been so ; and it is impossible to 

 avoid the conclusion, that if it had been otherwise, if no other tem- 

 perature but what we have had so often to refer to as the G tempe- 

 rature had been indicated in their analyses, we should have profited 

 more by their labours, and been further advanced in the science of 

 heat and elastic fluids. 



^ LXXXI. Intelligence and Miscellaneous Articles. 



^N THE HYPOTHESES RELATING TO THE LUMINOUS iETHER, AND 



V AN EXPERIMENT WHICH APPEARS TO DEMONSTRATE THAT 



THE MOTION OF BODIES ALTERS THE VELOCITY WITH WHICH 



LIGHT PROPAGATES ITSELF IN THEIR INTERIOR. BY M. H. 



FIZEAU. 



MANY hypotheses have been proposed to account for the phseno- 

 mena of aberration in accordance with the doctrine of undula- 

 tions. Fresnel in the first instance, and more recently Doppler, Stokes, 

 Challis, and many others, have published memoirs on this important 

 subject ; but it does not seem that any of the theories proposed have 

 received the entire assent of physicists. In fact, the want of any defi- 

 nite ideas as to the properties of the luminous aether and its relations 

 to ponderable matter, has rendered it necessary to form hypotheses, 

 and among those which have been proposed there are some which are 

 more or less probable, but none which can be considered as proved. 

 These hypotheses may be reduced to three principal ones. They 

 refer to the state in which the aether existing in the interior of trans- 

 parent bodies may be considered to be. 



This Kther is either adherent, and as it were attached to the 

 molecules of bodies, and consequently participates in the motions to 

 •which the bodies may be subjected; 



, Or the ajther is free and independent, and is not influenced by the 

 motion of the bodies ; 



