14-^ BIRDLIMK. 



Birdlime of f able and animal matter ; fnmetimes it is even adulterated 

 ouenTy aduu' ^'''' turpentine, oil, vinegar, &c. It was therefore necef- 

 tcrated. fary that I (hould be certain as to its purity ; and by the fol- 



lowiiir mode, which I adopted, I obtained birdlime of the 



very bed quality. 

 Th-- author's Having procured a fufHcient quantity of the fecond bark of 



hours : tfie water being poured oiF, I depofited the bark in 

 pits, in earthen pans, where it remained till rotten, or at leaft 

 till it became vifcous, moiftenlng it from time to time with a 

 little water. When i( had obtained a proper degree of fer- 

 mentation, it was cleanfed, by wafhing, from all heteroge- 

 neous matters. 



Sect. II. 



Chemical and phyfical CharaBcriJiics of Birdlime. 



Charadleriftlcs. Birdlime is of a greenith colour, and of a four flavour : it is 

 gluey, ftringy, and tenacious. Its fmell refembles that of 

 linfeed oil. 

 It becomes dry Spread on a glafs plate, and expofed for fome time to the 

 expof "re toth ^^'"" of air and light, it dries, and becomes brown in colour, 

 airj being no longer vifcous. When quite dry, it may be re- 



duced to powder, in which ftate it is totally diverted of its 



but vifcid again adhefive qualities, and only recovers them on the addition of 

 v,hen wetted. ^^^^^^ 



Birdlime reddens tindure of turnfole. 

 By moderate When gently heated in a porcelain veflel it melts, but does 



beatitfues, ^^^ become rery liquid; it fwells in bubbles, which float 

 upon the furface. This kind of fufion produces fmall black 

 grains, which render the birdlime grumous : it produces a 

 fmell very fimilar to that obtained from animal oils, on raiting 

 their temperature. 



If this fiition be continued for fome time, the birdlime 

 aflumes a brownifh colour ; but recovers its proper charac- 

 teriftics on cooling. 

 Strong beat in- Placed on red-hot coals, it burns with a brilk flame, an4 

 iiVMt iti creates a great deal of fmoke. 



Heated in a crucible of platina, it takes fire when the cru- 

 cible is red-hot ; produces a lively flame, which rifes to about 

 two decimetres, accompanied with a confiderable quantity of 



fmok«. 



