110 Mr. J. Gill on the Dynamical Theory of Heat. 



bearing the impress of correctness, should still be obviously 

 erroneous as applied to the working of the commonest steam- 

 engine. 



The current doctrine of thermo-dynamics assumes that all the 

 heat which passes from the fire to a steam-boiler takes the form 

 of molecular motion, or vis viva, in the steam, and that the work 

 performed is so much of this molecular motion given out by the 

 steam in its passage through the engine; consequently that the 

 steam must contain less heat or molecular motion after it has 

 done work than before, and that the quantity of heat which 

 disappears by being thus transformed into work is in the pro- 

 portion of the mechanical equivalent of heat, which experiment 

 has fixed at 772 lbs. raised one foot by a quantity of heat which 

 will raise the temperature of 1 lb. of water 1 degree of Fahren- 

 heit. According to this doctrine, molecular motion is transferred 

 from the fire to the steam, and a small portion of this molecular 

 motion is transferred from the steam to the work done, or trans- 

 formed into this work, by far the largest portion remaining in 

 the steam after the operation is finished. 



Like Seguin a quarter of a century back, and like M. Hirn of 

 Colmar very recently, I find in the condenser of the engine all 

 the heat originally contained in the steam, after allowing for 

 known losses; but, unlike M. Hirn, my reason will not allow 

 me to alter my views and to interpret facts to suit a theory, 

 however well supported by authority. I hope this open declara- 

 tion of partial dissent will not prevent my obtaining a fair hear- 

 ing while I endeavour to show that the observed facts are not ne- 

 cessarily discordant with sound theory, though in the brief space 

 to which I must here limit myself, my exposition must be very 

 imperfect ; but my chief end will be attained if my suggestions 

 should fortunately induce an unprejudiced reconsideration of the 

 subject by superior intellects. 



It may be well to remark here that I am quite convinced of 

 the general correctness of that part of the dynamical theory of 

 heat which treats of the conversion of work into the molecular 

 motion supposed to constitute heat in common matter ; and I 

 hope that science will soon clear up the obscurity which still enve- 

 lopes the converse phenomenon, or the change of heat into work. 



The material universe in its lowest or most external manifes- 

 tation, presents to a superficial glance only matter and motion. 

 On deeper investigation it is perceived that matter is under the 

 influence of principles of energy or force, or is endowed with such 

 principles which cannot be satisfactorily explained as general 

 results of motion, — though much ingenuity has been displayed in 

 attempting to account for the phenomena of terrestrial gravita- 

 tion as the result of the .earth's axial rotation and revolution in 



