APPARATUS FOR HEATING. 



15 



wide tubes they must be smoothed on a grindstone. For heating, 

 a spirit lamp is used, or coal gas where it is accessible. Two kinds 

 of spirit lamps are mostly in use : the simple spirit lamp (fig. 15) 



FIG. lo (f real size). 



FIG. 17 (^ real size). 



serves for smaller objects, or for moderate heating. For producing 

 very high degrees of heat a Berzelius's Argand spirit lamp is re- 

 quired, two varieties of which are shown in figs. 16 and 17. 



