$9 On the Union of Gases. 



with the silver, as usually praclistd in the manufacture of 

 that metal. Having, however, uniformly observed the green 

 light, from the purest silver leaf 1 could obtain, when defla- 

 grated either by an electrical or Voltaic battery, I did not 

 feel inclined to assent to ihi!» conclusion without lurther 

 trial; and was rather disposed to attribute the phsenoniena 

 then observed to some other cause. The construction of a 

 large Voltaic appara'us for the Lectures at the Scientific In- 

 stitution, soon afforded me an opportunity of verifying the 

 opinion I had form d. Having observed that Mr. Davy's 

 conducting wires were terminated by charcoal, I employed 

 a similar arrangement ; and applying the charcoal to pure 

 silver leaf, it immediately burned with 3 beautiful white 

 light. Some of the same portion of silver having been be- 

 fore employed, when the green flame was produced, it be- 

 came evident that the white light in this and in Mr. Davy's 

 experiment proceeded from the charcoal : and that this was 

 really the case, appeared from the immediate evolution of 

 green light when the contact was made by a metallic wire. 

 By the application of charcoal to the extremity of a wire, 

 so bent that either the wire or charcoal may touch the 

 silver at pleasure, the white and the green flame may be 

 alternately produced; and a conclusive demonstration of the 

 fact, with a pleasing variation of a brilliant experiment, will 

 be thus at once afforded. 



XL 0?i the Union of Gases. 

 To Mr. Tillock. 



SIR, 



X HAVE sent you the inclosed for a place in your work, if 

 you think fit. An idea has struck me of a mechatiical union 

 of gas, which will not he liable- to any of the objections 

 raised against Mr, Dalton's, and which, I believe, will apply 

 to every phaenointnon. The principle is this, that from the 

 laws of elastic fluids, it will be found to follow, that if the 

 particles of one be lartrer than the panicles of another ; or 

 rather, if the repulsive sphere of one be greater than the re- 

 pulsive 



