DetonaiionSt £s*^. — Natural HiJ!ory of Gutana. 7gj 



the combuftion ; with charcoal and other vegetable fubftances, the carbonic acid ; with ful- 

 phuret of arfenic there may be fulpureous acid gas and arfenic acid produced. 



The fudden produftion of gas ftriking the furrounding air, is moft probably the caufe of 

 the loud reports produced by fri£lion, &c. agreeably to the conclufions of Berthollet ; and 

 the muriatic acid may remain combined with the potafti, and a portion of the combuftiblc 

 fubflance employed: but, when the fulphuric or nitrous acida are ufed, the muriatic acid is 

 certainly difeiigaged. 



Since the above experiments were made, I have found that a paper has been rea4 before 

 the National Inftitute of Paris, On detonation by concuffion, by Citizens Fourcroy and 

 Vauquelin *. They there mention fome of the mixtures 1 have defcribed, and their in- 

 flammation with the fulphuric acid. They likewife notice, that very loud reports and 

 fparks were produced, on a very fmall quantity of different mixtures being ftruck with a' 

 hammer on an anvil. This on trial I found to be the cafe; and a little cotton-wool well 

 impregnated with the fait being ftruck in that way immediately took fire. But, to get this^ 

 to fucceed, the fait and crftton fliould be perfeftly dry : this is a neceflary precaution [n all 

 experiments on the detonating property of this fait by fridlion, &c. In the paper abovfr 

 alluded to it is ftated, that fugar, the gums,fixed and volatile oils, alcohol and ether, do not 

 detonate or take fire by fimple trituration : but the experiments I made feem not to agree 

 with this afTertion ; for all the above fubftances that I tried, except ether, detonated either 

 more or lefs, on rubbing them brifkly in a ftone-ware mortar; fome of them required to be 

 intimately mixed, as fugar and gum ; but others produced very loud reports, as when fixed 

 and efTential oils were ufed. 



IV. 



Obfervatlons 6n the Natural Hijlory of Guiana. In a Letter from WiLLIAM LoCTlEADr 

 Efq. F.R. S. Edin. to the Rev. Dr. Walxer, F. R. S. Edin. Regius Profejor of Natural 

 Htflory in the Univerfty of Edinburgh f . 



Dear Sir, 



A 



LLOW me at prefent to trouble you with a few general obfervations on natiral 

 hiftory, which I had an opportunity of making while on a botanical excurlion, with my 

 friend Mr. Anderfon, to the Dutch colony of Demerary, Guiana is a country but little 

 known in Europe, though its animals and vejjetables have added confiderably to the cata- 

 logue of natural productions. It is not, however, the organic kingdom which I mean at 

 prefent to touch upon ; all I aim at is, to give you fome idea of the face of the country,, as 

 leading to the knowledge of its formation and prefent ftate. It is not a field for the mine- 

 ralogift, as its interior is unexplored. But to the geologift, who wifhes to trace revolutions 

 of the lateft date, it is not unintercfting to contemplate fuch a recent and fingular country 

 as Guiana. 



I need not inform you, that under Guiana is comprehended all the coaft of South Ame» 



• Annales de Chimie, torn. xxi. p, ^35. Nicholfon's Chemical Journal, i. p. 169. 

 f Edinburgh Traniafiions, iv. 



(ica^ 



