182 III. COMPOUND COMBUSTIBLES.— 



Gall stone, Calculus cysticus hovinus. From the gall bladder 

 of neat cattle in winter, when fed upon dry food ; used, gr. j, in 

 indigestions ; also as a yellow pigment. 



GELATINOUS EXTRACTS. 



Cake glue, Colle forte. Gluten commune. Prepared from the 

 sl<ins of animals, by soaking them for two or three weeks in lime 

 water, boiling them with water, adding a little alum, down to a 

 thick jelly, which is then poured out into shallow boxes, and, 

 when cold, cut into squares, and dried in the air upon nets ; used 

 as a cement. 



Flemish glue, Dutch glue. The skins are rinsed in several 

 waters, and left to soak for some time, that they may require less 

 boiling to be dissolved; cakes very thin, transparent ; used by 

 cabinet-makers in fine work. 



French glue. Simmered for a long time with a small fire, 

 until the skins are dissolved ; then made to boil, and alum gr. 

 ij. to the pint added, to clear it for moulding ; transparent and 

 very brittle. 



Hatmakers' glue. From the tendons of the legs of neat 

 cattle and horses; brown, opaque, soft; grows moist in damp 

 weather, but it does not render the felt brittle. 



Bone glue, Gelatine sec. From gelatine brut, pp. 186 and 

 138, by boiling it in water until dissolved, then moulding the 

 decoction into cakes to suit the market. 



Double size, Colle a baquet, Gelatine humide. Is made from 

 skins, mostly rabbit skins ; also old gloves, parchment, and gela- 

 tine brut, in the same manner as glue, but is not boiled down so 

 low, only so far that it is a tremulous jelly when cold. Single 

 size. Is not boiled down so low. 



Fish glue, Colle de poisson. Is made in like manner from 

 various membranous and solid parts of cetaceous animals. 



OF mineral origin. 



Cologne earth, CuUerCs earthy Umber ^ Terra Colonieiisis. 

 Black, or blackish brown, mixed with brownish red, fine grained, 

 earthy, smooth to the touch, becomes polished by scraping, very 

 light, burns with a disagreeable smell ; found near Cologne ; 

 used in painting, both in water-colours and in oil ; used also to 

 render snufF fine and smooth; very, different from the brown 

 ochre umber. 



