upon the Steam-Engine. S 
self to correcting such parts as appeared necessary, and to add- 
ing such matter as he had not an opportunity of knowing. 
Here it was my intention to have closed this letter ; but the 
representations of friends, whose opinions I highly value, induce 
me to avail myself of this opportunity of noticing an error into 
which not only Dr Robison, but apparently also Dr Black, has 
fallen, in relation to the origin of my improvements upon the ' 
Steam-Engine, and which not having been publicly controvert- 
ed by me, has, I am informed, been adopted by almost every 
subsequent writer upon the subject of Latent Heat. 
Dr Robison, in the article Steam-Engine, after passing an 
encomium upon me, dictated by the partiality of friendship, 
qualifies me as the pupil and intimate friend of Dr Black ;” 
a description which, not being there accompanied with any infe- 
rence, did not particularly strike me at the time of its first peru- 
sal. He afterwards, in the dedication to me of his edition of 
Dr Black’s Lectures upon Chemistry, goes die length of sup- 
posing me to have professed to owe my improvements upon the 
Steam-Engine to the instructions and information I had receiv- 
ed from that gentleman, which certainly was a misapprehension, 
as, though I have always felt and acknowledged my obligations 
to him for the information I had received from his conversation, 
and particularly for the knowledge of the doctrine of Latent 
Heat, I never did, nor could^ consider my improvements as ori- 
ginating in those communications. He is also mistaken in his 
assertion, p. 8. of the Preface to the above work, that “ I had 
attended two courses of the Doctor’s Lectures for, unfor- 
tunately for me, the necessary avocations of my business pre- 
vented me from attending his or any other lectures at College ; 
and as Dr Robison was himself absent from Scotland for four 
years at the period referred to, he must have been misled by 
erroneous information. In page 184 of the Lectures, Dr Black 
says, “ I have the pleasure of thinking that the knowledge we 
have acquired concerning the nature of elastic vapours, in con- 
sequence of my fortunate observation of what happens in its 
formation and condensation, has contributed in no inconsider- 
able degree to the public good, by suggesting to my friend Mr 
• Repeated more in detail, with the same erroneous inferences, in his note. 
