LESLIE. 79 



has been accused of having plagiarized this invention either from 

 Van Helmont, who died in 1644, or from John Christopher Stunnius, 

 who died sixty years later, he at all events showed, by his skilful 

 and fruitful employment of the disputed invention, how much he 

 surpassed, and how little he needed the help of, him whom he is 

 ungenerously supposed to have robbed of his legitimate honours. 



In 1800 he wrote several papers, on different branches of physics, 

 in Nicholson's ' Philosophical Journal,' which resulted in the publi- 

 cation at London, in 1804, of his ' Experimental Inquiry into the 

 Nature and Propagation of Heat.' The originality and boldness of 

 the peculiar doctrines contained in this work, and the number of 

 new and important facts disclosed by its ingenious experimental 

 combinations, rendered it an object of extraordinary interest in the 

 scientific world. The Koyal Society of London unanimously ad- 

 judged to its author the Rumford medal ; and although paradoxical 

 in many of its theories, defective in arrangement, and over ambitious 

 in style, this work is almost unrivalled in the entire range of physical 

 science, for its indication of vigorous and inventive genius. 



Previous to this period of life, Leslie had appeared twice as a 

 candidate for an academical chair; first in the University of St. 

 Andrew's, afterwards in that of Glasgow ; but on both occasions 

 without success. He now became a candidate for the Mathematical 

 chair at Edinburgh, vacant through the promotion of Professor 

 Playfair to the chair of Natural Philosophy. After a severe contest, 

 during which much party spirit was displayed, owing to his prin- 

 cipal competitor, Dr. Thomas Macknight, one of the ministers 01 

 Edinburgh, being supported by the majority of the city clergy, 

 Leslie was, in March, 1805, elected to the Mathematical chair. He 

 entered immediately upon his official duties, which he continued to 

 discharge with zeal and assiduity during the following fourteen 

 years. 



Notwithstanding the labours which these duties entailed upon 

 him, Leslie continued his experimental inquiries, and in June, 1810, 

 discovered his beautiful process of artificial congelation, by which 

 he was enabled to produce ice," and even to freeze mercury at 

 pleasure. The process consists of a combination of the powers of 

 rarefaction and absorption, effected by placing a very strong ab- 

 sorbent under the receiver of an air-pump. This experiment was 

 performed in London in 1811, before a meeting of some members of 

 the Royal Society ; and the discovery was announced in the same 

 year in the 'Memoirs' of the French Institute. He explained his 

 experiments and views on this subject in 1813, in a volume pub- 

 lished at Edinburgh, entitled, ' A short Account of Experiments 

 and Instruments depending on the Relations of Air to Heat and 

 Moisture.' Closely connected with the subject of this treatise 

 was an ingenious paper, published in 1818, in the ' Transactions' of 

 the Royal Society of Edinburgh, under the title, ' On certain Im- 



