02 PLYMOUTH INSTITUTION. 



June 12th. — Mr. Hearder's Lecture on Combmtion. 



The lecturer commenced by giving a brief definition of the term 

 Combustion, and a detail of the conditions necessary for its exis- 

 tence. He proceeded to show by experiments the beautiful 

 diversity which characterizes the developement of its various 

 phenomena ; and, after examining the different theories which 

 have been advanced from time to time in explanation of them, 

 went on to show some of its most interesting modifications. In 

 the course of the lecture, Mr. H. detailed some new and very 

 curious discoveries, which he had himself made very recently, 

 during his researches, on this particular branch. As the lecturer 

 entertained the idea that flame was nothing more than gaseous or 

 volatilized matter, at a very high temperature ; he concluded that 

 it must be subject to all the different modifications of contraction 

 or expansion which characterize other gaseous matter, and was 

 tlierefore led to institute a series of experiments in order to ascer- 

 tain the effect of pressure on the production or existence of flame ; 

 accordingly he inclosed in a receiver, connected with a very pow- 

 erful air pump, a portion of a mixture of chlorate of potass and 

 loaf sugar, which, by means of a slider passing air tight through 

 the cover of the receiver, could be brought into contact with a fine 

 piece of platina wire, which was kept at an intensely white heat 

 by a powerful galvanic current, transmitted through it by means 

 of forceps which were insulated through the same brass cover. 

 The air was then exhausted, and, on bringing the mixture into 

 contact with the hot wire, it merely melted into a brown mass at 

 those parts immediately in contact with the wire, but did not 

 ignite. On readmitting the air, however, the mixture burned 

 with its usual intensity. 



The lecturer stated that he had tried gunpowder and other such 

 substances with just the same effect; he concluded by stating 

 that he did not then feel himself prepared to offer any explanation 

 of these phenomena, as they were contrary to what he had expec- 

 ted, but that it was his intention to investigate the subject more 

 fully ; and that he would bring the result of his labours, together 

 with his opinions, before the society during the ensuing winter 

 session. 



