14 A Tribute to the Memory of 



Besides the lectures on the general principles of chemistry, 

 Mr. Henry delivered a course on the aits of bleaching, dyeing, 

 and calico-printing ; and to render this course more extensively 

 useful, the terms of access to it were made easy to the superior 

 class of operative artisans. It was at this period, that the prac- 

 tical application was made in France of a philosophical disco- 

 very to one of the arts which Mr. Henry was engaged in teach- 

 ing, that shortened, by several weeks, the duration of its pro- 

 cesses. In 1774, Scheele, a Swedish chemist, distinguished by 

 the number and great importance of his contributions to chemi- 

 cal science, discovered, in the course of some experiments on 

 manganese, the substance known successively by the names of 

 dephlogisticated marine acid, oxy-muriatic acid, and chlorine. 

 During several years afterwards, its properties were not applied 

 to any practical use, until its power of discharging vegetable 

 colours suggested to M. Berthollet, of Paris, its employment in 

 the art of bleaching. The first successful experiments with that 

 view were made by M. Berthollet in the year 1786, and, with a 

 liberality which confers the highest honour upon him, he freely 

 communicated his important results, not only to his philosophi- 

 cal friends, but to those who were likely to be benefited by them 

 in practice. Among the former was Mr. Watt of Birmingham, 

 who happened at that time to be in Paris, and who was the first 

 person in this country to carry the discovery into effect, by 

 bleaching several hundred pieces of linen by the new process, 

 at the works of a relative near Glasgow. Mr. Henry also, hav- 

 ing received an indistinct account of the new method, but not 

 knowing precisely in what it consisted, immediately set about 

 investigating the steps of the operation ; and in this he was fortu- 

 nate enough to succeed. Soon afterwards, an attempt was made 

 by some foreigners, who themselves had acquired their informa- 

 tion from Berthollet, to turn the process to their own advantage, 

 by obtaining a patent ; and having failed in that, by applying 

 for a parliamentary grant of an exclusive privilege of using it 

 for a certain number of years. Against the former, a strong 

 memorial, (which is now before the writer,) was presented by 

 Mr. Henry to the Attorney and Solicitor-General ; and effectual 



