DEC.] THE LABORATORY. 52c) 



long : the contents in ounce measures marked on 

 them with a diamond, beginning at top (when they 

 stand inverted, or the mouths downwards) 1, 2, 3, 

 &c. descending. These to receive and measure the 

 air or gas expelled by heat. 



Two or three old gun-barrels (the touch-hole 

 closed), cut to the length of eighteen inches, and a 

 small bent tube of iron, or of tin, finishing in an 

 iron screw, for screwing to the end of the barrel al- 

 ready mentioned. 



If a forge is not at hand, a cast-iron furnace, nine 

 or ten inches diameter, with a circular hole to receive 

 the gun-barrel, and a moveable dome cover to receive 

 the end of a tin pipe six inches diameter, and J2 feet 

 Ipng, and moveable while up the chimney of the 

 room. The fire to be of charcoal. 



A trough or small tub of water, on legs, adapted 

 in height to the elevation of the gun-barrel when in 

 the furnace, with a perforated shelf in it, on which 

 the jars to stand for receiving the air expelled. 



A correct pair of scales and weights. 



To try whether the gun-barrels or any retorts are 

 really air-tight, an air-pump is very useful, as I have 

 found that blowing in them when under water is not 

 a criterion to be depended on. 



An evaporating saucepan ; that is, a tin sauce- 

 pan with a circular fixed frame of tin, four inches 

 high, to receive a glass jar containing the earth to be 

 dried by the boiling heat of the water, as it is ne- 

 cessary in comparisons for all specimens to be of the 

 same degree of dryness. 



Pint or quart phials with ground stoppers of sul- 

 M m 2 phuric 



