On a Sulstaiice which lecomes a violet- coloured Gas ly Heat. 3 



D, should be so conveniently bent as to be held in the mouth 

 of the operator, who, in place of inhaling as before, will now 

 have to keep up a constant nourishment to the flame by occa- 

 sionally blowing in through this tube and thus forcing the 

 water to ascend into B ; whence it will act by pressure as be- 

 fore, the cock E being left open for that purpose. It will in some 

 degree assist the power if, in the intervals of blowing, the 

 tongue or lips be so managed as to stop the superior aperture 

 of this tube. But as Mr. Tilley's instructions are before your 

 readers I shall not intrude further rgsjiecting this part of my 

 subject. 



I am not aware that any contrivance of the same description, 

 and one that admits of such facilities in the construction, for 

 feeding the blow-pipe by inhalation has ever been employed, 

 otherwise I should not have troubled you with this commimi- 

 Cf^ion for public notice. 



I remain, sir. 



Your very obedient servant, 



Joseph Mume. 

 To Mr. Tilloch. 



II, Some Exljeriments and Olfservations on a new Substance 

 which lecomes a violet-coloured Gas ly Heat. By Sir 

 Humphry Davy, K?it. LL.D. F.R.S.* 



J:\. NEW and a very curious substance has recently occupied the 

 attention of chemists at Paris. 



This substance was accidentally discovered about two years 

 ago by !\'I. Courtois, a manufacturer of saltpetre at Paris. In 

 his processes for procuring soda from the ashes of sea weeds, 

 {cendres dc vareck) ho found the metallic vessels much corroded; 

 and in searching for the cause of this effect, he made the dis- 

 covery. The suljstaiice is prccurtd from the ashes, after the 

 extraction of the carbonate of soda, with great facility, and 

 merely by the action of sulphuric acid : — when the acid is con- 

 centrated, so as to produce much heat, the substance appears 

 as a vapour of a beautiful violet colour, which condenses in 

 crystals having the colour and the lustre of plumbago. 



M. Courtois, soon after he had discovered it, gave specimens 

 ot It to iMM. Uesormes and Clement for chemical examination ; 

 and those gentlemen read a short memoir upon it, at a meeting 

 of the Imperial Institute of France, on Nov. 29th. In this me- 

 moir, these able chemists have described its principal properties; 

 they mentioned that its specific gravity was about four times 



* From the Philosophical Transactions for 1814, part i. 



A 2 that 



