364 Dr. Prout on the ultimate composition 
tops of the larger tubes, 1 1, are cemented the vertical stop- 
cocks, M M, of which fig. 2. Plate XV, is a sectional view on 
a larger scale, and which renders the construction so obvious, 
that perhaps no further remark is necessary, than merely 
stating that the cup, a, is filled with oil, and that the plug, b, 
which is square at the upper part, and adapted to a key, is 
furnished with a shoulder, on which the screw-cap, c, rests, 
and by means of which it may be tightened at pleasure.* 
On the platform, FF. (fig. 1.) is a thin piece of wood, 
capable of being raised or depressed at pleasure, by means of 
the screws, O O ; on this the lamp O is placed, which may 
thus be placed at any distance that may be required from the 
tube, P. Fig. 3, is an enlarged view of this lamp : it consists 
of two reservoirs, de , for holding the spirit, connected toge- 
ther by means of the tube, f, into which are placed, at the 
distance from one another of about i of an inch, a number of 
vertical burners, g g, &c. about ~ °f an * n diameter, and 
~ inch long, and made as thin as possible, with the view of 
preventing the conduction of the heat. These burners are 
each furnished with a few threads of cotton, and are bent a 
little alternately like the teeth of a saw, in order that their 
flame may envelope the tube, P, ( fig. 1 . ) more completely. 
h is a cover for the wick of the lamp when not in use. The 
* These syphons are fixed together independently of the general frame work, 
and may be removed at pleasure by taking out the pins c d, c d, and e f, ef. This 
admits of their being replaced by others of different sizes. Those of a larger 
size have balls near the top, as represented by the dotted lines, and may contain as 
much as 20 cubic inches of gas. It much facilitates the process of determining 
the exact quantity of gas contained in the apparatus, to have both legs of the 
syphon graduated, which may be easily done so as to obviate the effects of capillary 
attraction when the tubes are not both of the same calibre. 
