320 Mr Drummond's Apparatus for producing 



inversely proportional to the minute state of division in which 

 the particles of lime are combined, it is highly probable that 

 denser kinds of wood, in which the pores are very small, 

 might leave after combustion a residue in which the lime ex- 

 ists in a much more attenuated state than that which I used, 

 and, therefore, the same intensity of light might be evolved 

 at a temperature still lower than that which exists at the edge 

 of a common flame. If this should turn out to be the case, 

 the light of the lime and the magnesia might be developed at 

 a temperature lower than that which discharges the phospho- 

 rescent light of minerals, and it might have a most extensive 

 and useful application, both in the arts and in domestic eco- 

 nomy. Even in the present state of the fact the subject de- 

 serves farther investigation. 11 



In order to obtain an intense light for facilitating the ob- 

 servation of distant stations in geodetic operations, Mr Drum- 

 mond endeavoured to make use of some of the most brilliant 

 pyrotechnical preparations, and to try phosphorus burning in 

 oxygen ; but he found in these cases the flame large and un- 

 steady, and unfit for a focal light ; and he was therefore led 

 to try the brilliant light emanating from several of the earths 

 when exposed to a high temperature. Having completed an 

 apparatus for this purpose, he produced a light so intense, 

 that, when placed in the focus of a reflector, the eye could 

 with difficulty support its splendour, even at the distance of 

 fortv feet. 



" In order to obtain the requisite temperature, 11 says Mr 

 Drummond, " I had recourse to the known effect of a stream 

 of oxygen, directed through the flame of alcohol, as a source 

 of heat, free from danger, easily procured and regulated, and 

 of great intensity. Fig. 2. of Plate VIII. represents the ap- 

 paratus such as it is now made for the survey. The spirit 

 entering at a, ascends through the tubes t, while the oxygen 

 entering at d is directed by the jets f upon the small ball of 

 lime b ; the tubes V are connected with the cylindrical box h 

 by flexible caoutchouc tubes e, f, and also pass with friction 

 through small cylinders at c, which admit of being moved 

 backwards and forwards upon the arms, and are clamped, 

 when in the proper position, by small mill-headed screws at the 



u 



