3C PROCEEDINGS OF THE 



if we search back for earlier conceptions of the identity of heat and motion, we 

 shall find (as we always do in such cases) that similar ideas have been held 

 before, though in a clouded and undemonstrated form. In the writings of Lord 

 Bacon we find it stated that heat is to be regarded as motion and nothing else. 

 In dilating upon this subject, that extraordinary man shows that he had grasped 

 the true theory of heat to the utmost extent that was compatible with the state 

 of knowledge existing in his time. Even Aristotle seems to hi.ve entertained the 

 idea that motion was to be considered as the foundation not only of heat, but of 

 all manifestations of matter; and, for aught we know, still earlier thinkers may 

 have held similar views. 



The science of gunnery, to which I shall make but slight allusion on this 

 occasion, is intimately connected with the dynamical theory of heat. "When 

 gunpowder is exploded in a cannon, the immediate effect of the affinities by which 

 the materials of the powder are caused to enter into new combinations, is to 

 liberate a force which first appears as heat, and then takes the form of mechanical 

 power communicated in part to the shot and in part to the products of explosion 

 ■which are also propelled from the gun. The mechanical force of the shot is 

 reconverted into heat when the motion is arrested by striking an object, and this 

 heat is divided between the shot and the object struck, in the proportion of the 

 work done or damage inflicted upon each. These considerations recently led 

 me, in conjunction with my friend Capt. Noble, to determine experimentally, by 

 the heat elicited in the shot, the loss of effect due to its crushing when fired 

 against iron plates. Joule's law, and the known velocity of the shot, enabled us 

 to compute the number of dynamical units of heat representing the whole me- 

 chanical power of the projectile, and by ascertaining the number of units devel- 

 oped in it by impact, we arrived at the power which took effect upon the shot 

 instead of the plate. These experiments showed an enormous absorption of 

 power to be caused by the yielding oature of the materials of which projectile! 

 are usually formed ; but further experiments are required to complete the inquiry. 

 * # * * « 



Few sciences have more practical value than meteorology, and there are few 

 of which we as j^t know so little. Nothing would contribute more to the saving 

 of life and property, and to augmenting the general wealth of the world, than the 

 ability to foresee witti certainty impending changes of the weather. At present 

 our means of doing so are exceedingly imperfect, but, such as they are, they have 

 been employed with consideiable eflect by Admiral FitzRoy in warning mariners 

 of the probable approach of stoi>ng. We may hope that so good an object will be 

 effected with more unvarying suctx^ss when we attain a better knowledge of the 

 causes by which wind and rain, heii, and cold are determined. The balloon 

 explorations conducted with so much Jitrepidity by Mr. Glaisher, under the 

 auspices of the British Association, may peihaps in some degree assist in enlight- 

 ening us upon these important subjects. We have learnt from Mr. Glaisher s 

 observations that the decrease of temperature wV;h elevation does not follow the 

 law previously assumed of 1<? in 300 feet, and tha* in fact it follows no definite 

 law at all. Mr. Glaisher appears also to have ascertianed the interesting fact 

 that rain is only precipitated when cloud exists in a double. layer. Bain-drops, he 



