M. Arago's Biographical Memoir of James Watt. 233 



be very great, it is to be attributed mainly to the latent 

 caloric ; the thermometric and sensible heat forms but a small 

 portion of it. 



I shall probably have occasion, in the sequel, to return to 

 some of the other properties of steam. If I do not insist 

 upon them at present, it assuredly is not because I attribute 

 to this assembly the state of mind of certain students, who one 

 day observed to their mathematical professor, " Why are you 

 taking all this trouble to demonstrate these theorems ? We 

 repose entire confidence in you ; give us only your word of 

 honour, and that will sufl&ce." But I feel anxious not to 

 abuse your patience ; and I ought also to remember that, by 

 I'eferring to particular treatises, you will readily svipply the 

 omissions which I shall find it impossible to avoid. 



Let us now endeavour to assign the share of merit which is 

 due to the several nations and individuals who should be enu- 

 merated in the history of the steam-engine, and trace the 

 chronological series of improvements which this machine has 

 undergone, from its first rude conceptions, now somewhat an- 

 tiquated, down to the discoveries of Watt. I approach this 

 inquiry with the firm determination of being impartial, — with 

 the most earnest solicitude to bestow on every improver the 

 credit which is his due, — and with the fullest conviction that 

 I am a stranger to every consideration unworthy of the com- 

 mission you have conferred upon me, or beneath the dignity 

 of science, originating in national prejudices. I declare, on 

 the other hand, that I esteem very lightly the innumerable 

 decisions which have ah'eady emanated from such prejudiced 

 sources ; and that I care, if possible, still less for the bitter 

 criticisms which undoubtedly await me, for the past is but the 

 mirror of the future. 



A question well propounded is half answered. If this sen- 

 timent, so full of truth, had always been kept in mind, the 

 discu.ssions concerning the invention of the steam-engine would 

 assuredly never have presented that character of acrimony 

 and violence which has hitherto been stamped upon them. 

 By seeking to discover a single inventor, where it was neces- 

 .sary to recognise many, we have been " in endless mazes lost." 

 The watchmaker who is most deeply versed in the histoi'y of hi.s 



