ANALYSIS OF THE YELLOW GUM. «jy 



tion of this acid, the residuum, being 37 parts, was a white, 

 dry powder, rough to the finger, and resembling fine sand. 



Ammonia, poured into the muriatic solution, separated 7 

 parts of oxide of iron; and oxalate of ammonia produced a 

 precipitate equivalent to 3 parts of lime. 



This chemical examination showsy that 100 parts of the 

 resinous cemeot are formed of 



Yellow resin 49 Its componeBt 



Pure sand •• 37 i^ant-, 



Oxide of iron 7 



Lime <.. 3 



Loss *••■ 4 



100 



It appears, that necessity has taught the natives of New 

 Holland a pratitice, which engravers employ every day. It 

 has taught them, to mix a proper quantity of sand with the 

 yellow resin kept some time in fusion, and thus to compose 

 a cement capable of acquiring considerable hardness. 



This is the mode in which the resinous cement, called in Siniilar to«B 

 the shops engravers' wax, is prepared. Brickdust is added S-^"^''' ^^s» 

 to common resin : the mixture is melted, and cast in moulds- 

 and thus it is formed into red cakes, which are sold to the 

 engravers. I have satisfied myself, that, the oftener this 

 mixture has been melted, the harder it is. 



I examined engravers' wax in comparison with the ce- 

 ment of the savages of New Holland ; and 1 observed with 

 fcurprise, that the proportions of resin and brickdust were 

 precisely the same with those of the yellow resm and sand in 

 the cement I analysed. 



It appeared to me, however, that the engravers' wax, iut harder. 

 though very hard, particularly when it has been melted se- 

 veral times, is inferior in solidity to the cement of the natives 

 of ^ew Holland; a difference that may be ascribed to the 

 difference between the resins, and the greater or less force, 

 with which their particles cohere. 



XV. 



