_to slide in a groove 
light, the burner is 
of Magnetical and Meteorological Instruments. 321 
ivory disk, and through the latter passes, by a narrow ent, made 
for the purpose, the burner or support for the wick, which is flat, 
half an inch wide and one-eighth of an inch in thickness. Com- 
mou ball cotton may be used for the wick, by drawing as many 
lengths through the burner as fill it closely, but not tightly. A 
movable ring or collar with a set screw, allows the burner to be 
fixed at any required height, while, the stopper being movable, 
it can also be turned to form any required angle with the face of 
the lamp. Let us then suppose the lamp to be placed behind a 
Screen containing a 
harrow vertical slit 
through which the 
light is to pass, and 
So as to be always 
presented in precise- 
y the same _posi- 
tion; let us suppose 
so the screen in 
question to be fixed 
supports the lamp. 
0 begin, then, with 
the regulation of the 
first to be fixed at 
such a height that 
the top of the wick a. Lamps and chimney.—. Ring placed under the chim- 
shall be exactly lev- ney to cut off strong light.—e. Section of lamps, shewing the 
el with the bottom burner (e) and the diaphragm in the chimney. 
of MM slit; it is then to be turned in azimuth so as to be pre- 
sented edzewise at an angle of about 80° with the screen, or 
at such an angle as to give a cone of rays very slightly wider 
than the mirror. The support of the chimney of the lamp is 
then to be applied, and its height regulated so that the dia- 
phragm by which the combustion is promoted, sha be about — 
0:10 inch below the top of the wick. Lastly, the chimney is 
added to the support, and the adjustments of the lamp are com- 
pleted by applying the short cylindrical shade which fits under 
the legs of the chimney, and prevents all lateral diffusion of 
the light. ‘The employment of camphine, although desirable on 
grounds of economy, as well as for the brilliancy and whiteness 
of its light, is atteuded with serious inconveniences. The fluid 
deteriorates very rapidly at summer temperatures ‘by the absorp- 
tion of oxygen, which converts a portion of the camphine into 
resin, which is held in solution in the remainder, and is deposited 
on the wick,’ in fact it becomes perfectly useless ; unless, therefore, 
Srconp Serres, Vol. IX, No. 27.—May, 1850. 41 
