44 Dr. Hare's Letter to Prof. Faraday 



and if the light is equal to that afforded by the rectangular 

 shouldered ones, they should be preferred. 



One more point, which was barely touched upon by Sir J. 

 Herschel, yet remains to be decided : Is this superior splen- 

 dour of the flame attended by an increased consumption of 

 oil? If we reasoned from analogy, we should certainly 

 reply in the affirmative ; intensity of combustion being ever 

 attended with corresponding consumption of the combustible 

 material. But to place this beyond a doubt, the following 

 experiment was undertaken. Two Argand lamps, having 

 wicks and chimneys of the same diameter and length, and 

 furnished with the same kind of oil, were placed in a pair of 

 scales, each at an equal distance and elevation from the centre 

 of a sheet of white paper pasted on the wall. On being lighted, 

 the flames were regulated till the shadows cast by a small 

 ruler had an equal depth ; when this had been fairly deter- 

 mined both by myself and others, weights were put into the 

 stand containing the lighter lamp, till the two exactly ba- 

 lanced each other. The chimney was now quickly removed 

 from one of the lamps, and another substituted for giving a 

 clear white flame, the time being at the same moment noted: 

 they were allowed to burn for forty-two minutes, and were then 

 simultaneously extinguished. At the expiration of this time, the 

 lamp burning with the bright flame had consumed 100 grains 

 more than the other. The experiment being repeated, but 

 with smaller flames, the increased consumption of oil in the 

 bright burning lamp was 50 grains. Whether this greater 

 expenditure of oil is balanced by the increased degree of 

 illumination, and the solution of some other interesting ques- 

 tions connected wit h this subject, I shall reserve till a future 

 period. I am, Gentlemen, 



Your obedient Servant, 

 13, Keppel Street, Russell Square, C. HoLTHOUSE. 



April 11, 1840. 



IX. A Letter to Prof. Faraday, on certain Theoretical Opi- 

 nions. By R. Hare, M.D., Professor of Chemistry in the 

 University of Pennsylvania *. 



Dear Sir, 

 1. HAVE been indebted to your kindness for several 

 J- pamphlets comprising your researches in electricity, 

 which I have perused with the greatest degree of interest. 



* From Silliman's American Journal of Science and Arts. Vol. 38, No. I. 

 [We have taken the liberty of numbering the paragraphs of Dr. Hare's 

 letter.— Ed.] 



