Mr DrummoncTs Apparatus for producing Intense Light. '310 



Art. XXII. — Description of an Apparatus for producing In- 

 tense Light, visible at great Distances, invented by Lieu- 

 tenant Thomas Drummond of the Royal Engineers. 



The memoir from which the following article is taken, is en- 

 titled On the Mea?is of Facilitating the Observation of Distant 

 Stations in Geodetical Operations. It was read before the 

 Royal Society of London on the 4th of May 1826, and will 

 appear in their Transactions for the present year. 



It has been long ago observed by those who have been in 

 the habit of using the blowpipe, that lime and other earths 

 give out a very intense and dazzling light when exposed to the 

 action of that instrument. 



The idea of applying this kind of light to economical and 

 useful purposes, seems to have been first published in a notice 

 on a singular luminous property of wood steeped in solutions 

 of lime and magnesia, written by Dr Brewster in 1820, and 

 printed in vol. iii. p. 343, of the Edinburgh Philosophical 

 Journal. 



" The sight of these experiments (it is there remarked) na- 

 turally suggests the idea, which occurred also to Mr Cameron, 

 that such a brilliant light, capable of being developed by the 

 heat of the flame of a candle,might have some useful application. 

 In order to obtain some information on this point, I prepar- 

 ed three or four pieces of wood, terminated with the white 

 masses of absorbed lime, and placed these masses so as to re- 

 main near the circumference of the flame of a candle. In this 

 situation they yielded the brilliant light already described, and 

 lasted, without any apparent diminution, for more than two 

 hours. I next prepared a very thin slice of chalk, and having 

 held it on the flame of a candle, I found that it did not give 

 the same brilliant light as the absorbed lime. Upon expos- 

 ing it, (the chalk) however, to the heat of the blowpipe, it 

 emitted the same white and dazzling light, which has already 

 been described ; (namely, a brilliant dazzling light, not much 

 if at all inferior to that which arises from the deflagration of 

 charcoal by the action of galvanism.' 1 '') 



" As this light seems to be developed by degrees of heal 



