126 MOHR AND REDWOOD'S PRACTICAL PHARMACY. 
finally for warming the shop. The means of applying it 
for the three first-named purposes, will be described under 
the head of Steam Apparatus for the Laboratory." 
a Gas and Alcohol Lamps . — In the greater number of dis- 
pensing establishments the range of operations requiring 
heat is very limited, and the space for operating confined 
chiefly to the shop. To these the possession of gas, and 
alcohol lamps, is invaluable. Where gas is to be had, gas- 
burners should be used in preference to all other lamps, as 
safer, more economical, and far more conveniently managed. 
" Gas has long been used for Fig. 18. 
heating purposes, but its smoki- 
ness was a serious objection to 
its use until the suggestion of 
Dr. Duncan, of Edinburgh, was 
carried into practice. This con- 
sists in burning it after admix- 
ture with atmospheric air. A 
wire gauze is stretched across the 
top of a tinned iron cylinder, into 
which, at its lower and open end, 
the gas enters from a jet and 
mixes with the air as it rises. The 
mixture is ignited above the 
gauze and burns with a clear 
bluish flame. Fig. 18 shows the 
manner in which this is effected. 
"The original cylinder of Sir A. 
Robinson was thirty inches long, 
but it has been found that six or 
eight inches is quite long enough; 
and if several diaphragms of 
coarser wire gauze be placed a t 
intervals in the cylinder, its length may be decreased 
to four inches ; especially if the gas issues into the cylinder 
from such a burner as fig. 19. 
