99 Mr, Brande’s chemical Experiments on Guaiacum, 
principle, and as such, perhaps the definition of it by the term 
of an Extracto-Resm may be adopted without impropriety. 
P. S. I have observed that the action of oxygen on some 
of the other resinous bodies is very remarkable. It is well 
known that by digesting mastich in alcohol, a partial solution 
only is formed, and there remains an elastic substance, which 
is generally said to possess the properties of pure caout- 
chouc ; it appears however to differ from this substance in 
becoming hard when dried by exposure to air. Moreover, I 
have remarked that the part of mastich which remains dis- 
solved by alcohol, may be again precipitated by water, and, 
on examination, I found the precipitate to possess the properties 
of a pure resin : but when a stream of oxy-muriatic acid gas 
was made to pass through the solution, a tough elastic sub- 
stance w 7 as thrown down, which became brittle when dried, 
and was soluble in boiling alcohol, but separated again 
as the solution cooled : its properties, therefore, somewhat 
approached to those of the original insoluble part. 
