206 Mr. Deuckar*s Remarks [March, 



Article IX. 



Remarks regarding the Experiments upon Flame, performed with 

 the Apparatus Tor discharging Ordnance without the Use of a 

 Jjight or Match-Lock. By Mr. John Deuchar, Lecturer on 

 Chemistry in Edinburgh. 



(To the Editor of the Annals of Philosophy/.) 



SIR, 27, Lothiaii-sircct^ Edinburgh, Feb. 10, 1821. 



At a metting of the Wernerian Natural History Society, 

 which was held to day, I read the continuation of my account of 

 the experiments performed with the apparatus for discharging 

 ordnance, a description of which was given in the last number of 

 the Annals. In this paper T have entered upon the cause of the 

 results which present themselves. 1 have endeavoured to show 

 by experiments that it is not in the slightest degree electrical, 

 but that it may, with more propriety, be ascribed to free caloric 

 in a so far insulated or condensed state. I have not yet tried the 

 whole of the experiments I had chalked out to myself; for the 

 proof of this, so far, however, as I have gone, they verify the 

 •onclusion. I have also noticed more fully the nature of the 

 flame while in rapid motion, and the alterations of its effect 

 upon substances by retarding that movement ; when its force is 

 not retarded, it passes through many inflammables without 

 affecting them in the least ; but when its velocity is so far stop- 

 ped as to bring it for a longer time in contact with the substance 

 to be acted upon, then it begins to display, in a greater or less 

 degree, the usual effects of caloric. 



As you will find the minute details of these experiments in the 

 third volume of the Transactions of the Wernerian Natural His- 

 tory Society, to be published in a few days, I should not have 

 troubled you with any observations at present, had it not been 

 that from what was mentioned at p. 93 of the present volume of 

 the Ajinals, regarding the experiments with wire gauze, it might 

 appear that the gunpowder could not be fired through the wire 

 gauze used in Sir H. Davy's safety lamp, vvithout the wire being 

 injured. I have since found that the wire gauze I bought of the 

 manufacturer, and which he assured me was the same as that 

 used in the safety lamp, was by far too fine, and that it was on 

 this account the flame sometimes forced away a part of it. The 

 following experiments, which I extract from the paper above 

 alluded to, will remove any misconception that may have arisen 

 on this part of the investigation. The wire gauze I used was 

 made of brass ; an inch of the finest kind contained 70 meshes 

 in the length, being 4,900 in the square ; and the coarsest kind 

 contained 36 in the length, being 1,296 meshes in the square 



