vm 



of great interest and importance in modern science, is his determination 

 (the earliest of any real value) of the absolute conductivity of a substance, 

 i. e. how much heat passes per second per unit of surface through an 

 iron plate of given thickness, whose faces are maintained at constant given 

 temperatures. As a proof of the value attached by scientific men to 

 these ingenious experiments, it is only necessary to mention that the 

 British Association has given a grant for their repetition with the best 

 attainable instrumental means, and for their extension to other substances 

 than that to which Forbes was obliged to confine himself. 



But on his more active work an arrest was soon to be laid. In De- 

 cember 1851 he was prostrated by a severe hemorrhage in the lungs, 

 occasioned, it was thought, in part by exposure on the Alps, in part by 

 too close application while prosecuting further experiments on heat. For 

 two Sessions and a half he was entirely laid aside from work. In the 

 winter of 1854 he resumed his duties, but daily lecturing was a heavy 

 burden on his now enfeebled strength. As for exploration or continuous 

 experimenting, all that was ended. 



" Though he could not leave Edinburgh without some natural pangs, 

 yet," continues Principal Shairp, " it was no doubt a relief to him when 

 he was called to assume the Principalship of this College [St. Salvador 

 and St. Leonard's United College, St. Andrew's] in the beginning of Session 

 1859—60. The office fitted in better to his state of health, because it 

 relieved him from the necessity of giving daily lectures, and set him more 

 free to do his work at the hours and in the way that suited him. He was, 

 however, far from regarding it as a sinecure, as some speak. Our late 

 Principal was not the man to regard any post of trust as a sinecure. 

 He came among us, no doubt, with diminished strength. But illness 

 had not abated his mental energy. Few men felt more the appeal which 

 the past history and present aspect of this city makes to the imagination. 

 But though much captivated with this, he found on his arrival enough of 

 hard matter-of-fact work ready to his hand, and into it he threw himself 

 vigorously." 



" Those who were comparatively strangers to our late Principal ob- 

 served in him a certain antique formality and reserve which they sometimes 

 mistook for coldness. They little knew how gentle and affectionate a 

 heart lay under that exterior— what longing for sympathy, what apprecia- 

 tion of confidence and frankness in others. His thoroughness in all work, 

 his painstaking in the most ordinary college business, his patience in 

 getting to the bottom of every minutest detail — as great, indeed, as if it 

 had been a link in some grave discovery — these are things which only his 

 colleagues can know." 



" His last public act, I believe, was to preside at the laying of the 

 foundation-stone of the new College Hall Building in 186/. A few days 

 after, he left St. Andrew's not to return. The sequel in its outward de- 

 tails (that winter abroad, the return to Clifton, and the close) would be too 

 painful to dwell on. But while his body was reduced to the last stage of 



