1818.] Scientific Intelligence. 305 



author of this ingenious contrivance, it seems, is yet unknown,* 

 although your readers must be well aware that it is an extension 

 of Sir Humphry Davy's experiment with ether. An accidental 

 conversation in Mr. Cary's shop in the Strand, enabled Mr. 

 Holme to bring to Cambridge intelligence of the curious, not to 

 say important use, which had been made of Sir Humphry's 

 discoveiy. We succeeded in the first trial we made ; and a 

 lamp thus ignited was exhibited in my lecture room, before the 

 gentlemen of the University, where it continued burning during 

 many hours. But I had no idea, at the tune, of the degree of 

 light and heat which this aphlogistic lamp was capable of exhibit- 

 ing : and as many of your readers may yet remain as ignorant 

 of its powers as I was in my first experiments with it, I will 

 briefly state the method by which it may be made to evolve a 

 degree of light not only sufficient to enable a person to read the 

 smallest printed or written characters during the night, but 

 which radiates with the intense splendour of substances under- 

 going combustion in oxygen gas, and is attended by heat so 

 powerful that the alcohol takes fire, and the lamp becomes 

 spontaneously lighted within a few seconds after being extin- 

 guished. 



It has been already stated that the platinum wire for the 

 aphlogistic lamp, ought not to exceed -j-^ part of an inch in dia- 

 meter. Twelve coils of this wire (spirally twisted for the 

 purpose round the tube of a tobacco pipe), are to surround, six 

 the wick of the lamp, and six to remain elevated above the 

 wick. But, having this information, nine persons out of ten 

 may fail in their attempt ; or produce at best a feeble effect with 

 the lamp ; simply from the circumstance, either of their making 

 the diameter of the coils too large, or from twisting also into a 

 spiral form and confining by the pressure of the wire the cotton 

 wick. The wick should be small ; and quite loose in the burner 

 of the lamp ; and every fibre of the cotton should be placed as 

 perpendicularly as possible. The diameter of the coils should 

 be exactly -^ of an inch ; they should be as near to each other 

 as possible without touching, those which lie uppermost being- 

 closer together than the first spiral coils which rise from the top 

 of the wick. I succeeded best when there were six coils above 

 the wick and 9^ below, upon the wick. The light then given 

 out was too intense to be endured by the sight. A dark passage 

 was illuminated by it, and the alcohol was twice spontaneously 

 kindled in consequence, When the same lamp, after being 

 extinguished, became again ignited, in its aphlogistic state, i 

 read paragraphs from newspapers, and manuscript notes written 

 in a veiy small hand, by the light it afforded. 



I remain, &c. 



E. D. Clarke. 



• According to Mr. Cary't subsequent information, (lie invention of this lamp is 

 due lo Mr. Ellis, of Oath. 



Vol. XI. N° IV. U 



