MOHR AND REDWOOD'S PRACTICAL PHARMACY. 129 
is also an aperture extending from the bottom upwards to 
the height of about five inches, through which the flexible 
gas tube passes, and which admits of the lamp being placed 
on a block of wood, so as to bring the flame nearer to the 
lop of the furnace when this is desired. 
"But, of all the several kinds Fig- 22. 
of apparatus which have been 
suggested, I have found none so 
generally convenient and effi- 
cient as that represented at fig. 
22. This form of apparatus was 
contrived by Mr. Gilbertson, of 
Ludgate Hill, by whom it is sold. 
It consistsof a conical vessel (A), 
with a water-joint rim at the top, 
into which the cover E fits. A 
tube (D) is ground to fit into the 
opening in the bottom, and over 
the end of this tube is placed a 
conical tube (G), the lower end 
of which has several notches cut 
in it, so that the liquid can pass 
,. .' ... , , . Gilbertson's Displacement 
under it when placed as shown Apparatus. 
in the drawing. The lower extremity of the vessel A is 
ground to fit into the mouth of the receiver (B.) 
In using the apparatus, the cover (E) is removed, and 
some dry, clean sand is poured into the vessel A, so as to 
form a layer (F) at the bottom. Over this the solid ingre- 
dients to be operated upon (G) are carefully packed, and a 
layer of sand (H) is placed over these. The spirit (I) is 
then poured over the surface of the sand, care being taken 
not to disturb the ingredients below. The best method of 
guarding against the disturbance of the dry ingredients, on 
pouring the spirits in, is to place a flat cork(K) on the sand, 
and to direct the stream of liquid on to the cork, which will 
float on the surface of the liquid when introduced; the force 
