330 Lieut. Drummond on the means of facilitating the 
applying, to the purpose in view, the brilliant light emanating 
from several of the earths when exposed to a high temper- 
ature ; and at length I had the satisfaction of having an appa- 
ratus completed, by which a light so intense was produced, 
that when placed in the focus of a reflector the eye could with 
difficulty support its splendour, even at the distance of forty 
feet, the contour of the reflector being lost in the brilliancy 
of the radiation. 
To obtain the requisite temperature, 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. 4 
represents the apparatus 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 t' upon 
the small ball of lime b, the tubes t' are connected with the 
cylindrical box h by flexible caoutchouc tubes ef, 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 millheaded 
screws at the sides. By these means every requisite adjust- 
ment is obtained for the jets through which the gas issues. 
The apparatus is attached by its base to the stand which car- 
ries the reflector (fig. 3, Plate XII . ) and the small ball may 
then, by means of the horizontal and vertical screws r, be 
brought with great accuracy into the focus of the reflector. 
The cistern c containing the alcohol is placed behind the 
reflector (fig. 3,) and being connected with the stem a by a 
flexible caoutchouc tube, may be elevated or depressed on 
* Annals of Philosophy, vol. ii. p. 99. 
