6lO PHILOSOPHICAL TRANSACTIONS. [aNNO 1775. 



This power of generating heat seems to attend life very universally. Not to 

 mention other well known experiments, Mr. Hunter found a carp preserve a 

 coat of fluid water round him, long after all the rest of the water in the vessel 

 had been congealed by a very strong freezing mixture. And as for insects. 

 Dr. Martine* observed, that his thermometer, buried in the midst of a swarm 

 of bees, rose to 97°. It seems extremely probable, that vegetables, together 

 with the many other vital powers which they possess in common with animals, 

 have something of this property of generating heat. Dr. B. doubts if the sudden 

 melting of snow which tails upon grass, while that on the adjoining gravel walk 

 continues so many hours unthawed, can be adequately explained on any other 

 supposition. Moist dead sticks are often found frozen quite hard, when in the 

 same garden the tender growing twigs are not at all atFected. And many herba- 

 ceous vegetables, of no great size, resist every winter degrees of cold which are 

 found sufficient to fi-eeze large bodies of water. It may be proper to add, that 

 after each of the abovementioned experiments of bearing high degrees of heat, 

 they went out immediately into the open air, without any precaution, and 

 experienced from it no bad effect. The languor and shaking of their hands soon 

 went off, and they did not afterwards suffer the least inconvenience. 



XIII. The supposed Effect of Boiling on JVater, iti disposing it to Freeze more 

 readily, ascertained hy Experiments. By Joseph Black, M. D.,-\- Professor of 

 Chemistry at Edinburgh, p. 124. 

 " We had lately, says Dr. Black, one day of a calm and clear frost ; and I 



immediately seized the opportunity, which I missed before, to make some 



• E«says Medical and PhUosophical, p. 331. — Orig. 

 ' f This celebrated chemical philosopher was bom in 1728, at Bourdeanx, in France, of British 

 parents. He was sent for education first to Belfast, and afterwards to Glasgow, where he studied 

 physic and took the degree of m. d. He was afterwards appointed to read lectures on chemistry 

 and medicine in that university; and in 1766 Dr. Cullen having exchanged the professorship of 

 chemistry for that of the practice of physic in the university of Edinburgh; Dr. Black was appointed 

 to succeed hin> ; and the duties of this office he continued to discharge with increasing reputation for 

 upwards of 30 years. In this situation, says Professor Robison, he soon became one of the principal 

 ornaments of the university of Edinburgh, and his lectures were attended by a crowded audience. 

 It could not be otherwise. His personal appearance and manners were those of a gentleman, and 

 peculiarly pleasing. His voice in lecturing was low but fine ; and his articulation so distinct, that 

 he was ijerfectly well heard by an audience consisting of several hundreds. His discourse was so 

 plain and perspicuous, his illustration by experiment so apposite, that his sentiments on any subject 

 never could be mistaken ; and his instructions were so clear of all hypothesis or conjecture, that the 

 hearer rested on his coochisiDns with a confidence scarcely exceeded in matters of his own 

 experience. 



Dr. B.s constitution v»as never strong, and for many years preceding his death, he had been sul^ect 

 to a spitting of blood, which he had prevented fix)m proceeding to an alarming length by a very abste- 

 mioos diet and remarkable serenity of mind. His bodily strength, however, declined very visibly 



