|06 DESCRIPTION OF A BLOW-PIPE. 



the electricity excited on their furfaces by the friction, and 



partly by their phofphorefcence, which is generally occafioned 



Cafes of a&ual by moderate degrees of heat. It is not however improbable 



jsnition: ^^ * m fo me ca f es ^ by t j ie co p,ifi on f ver y hard ftony bodies, 



which are bad conductors of heat, there may be an actual ig- 

 nition of abraded particles; and the fuppofition is counte- 

 nanced by various facts. Mr. T. Wedgwood found that a 

 piece of window glafs, when brought in contact with a re- 

 volving wheel of grit, became red hot at its point of friction, 

 and gave off luminous particles which were capable of in- 

 flaming gunpowder and hidrogen gas *. And we are informed 

 by a late voyager f, that the natives of Oonalafhka light their 

 fixes by fir iking together two pieces of quartz, their furfaces 

 being previoully rubbed with native fulphur, over dry grafs. 



VIII. 



Defcription of a Blow-pipe by Alcohol, having afafety Valve, with 

 other Advantages. Conjirucled by Mr. Benjamin Hookh, 

 Fleet Street. 



To Mr. NICHOLSON. 

 SIR, 



Blow-pipe with i HAVE taken the liberty of troubling you with a drawing 

 •nl fe on*c V flIme ndand defcri P tion of the bloiv-pipe by alcohol as I make it, which 

 perhaps pofiefies the following advantages over that defcribed 

 in your number of September laft ; viz. Being furnifhed with 

 a fafety valve, to prevent accidents; having only one lamp 

 (the wick of which being pretty large, anfwers both for heat- 

 ing the alcohol and for affording a ftrong blafi: when drawn 

 through it) ; and I think fuperiority as to form and appear- 

 ance. 



Should you efteem it worthy a place in your valuable Jour- 

 nal, the infer tion will oblige, 

 SIR, 



Your very humble fervant, 

 159, Fleet Street, BENJAMIN HOOKE. 



Nov. 20, 1802. 



* Phil. Tranf. 1792, p. 45. 



f Sauer's Account of Billings's Expedition to the northern parts 

 ofRuflla, p. 159. 



A is 



