on naphthaline. 219 
nearly cool ; and the matrass being placed between the eye 
and a tolerably strong light, numerous transparent rhombic 
crystals will be visible ; some of them reflecting from their 
whole surface a green colour ; others, a blue ; or a red ; or 
some other of the prismatic colours. 
With respect to the elementary constitution of this sub- 
stance I am not enabled to give any satisfactory information ; 
but it is evident that it contains a very great proportion of 
carbon. A small quantity of it was passed in the state of 
vapour through peroxide of copper heated to redness, and 
the only gaseous product was carbonic acid : whether any 
water were formed, I could not ascertain. 
It cannot be irrelevant to the object of this paper to state, 
that the white concrete substance which I have been de- 
scribing, has twice been observed by me in the form of 
minute crystals, which beautifully reflected the prismatic 
colours, in the neck of an earthen retort, in which animal 
matter had been submitted to destructive distillation. 
Properties of the yellow farina. 
From the minute quantity of this substance which I was 
capable of obtaining, I could only ascertain one or two of its 
properties. It is soluble in alcohol, and forms a solution of a 
bright yellow colour ; and it is precipitable from the solution, 
by the addition of water, in the form of a yellow powder, 
which remains permanently suspended in the mixture. 
When heated, it melts into a substance of the consistence 
of a soft tough gum of a deep reddish brown colour. 
MDCCCXXI. 
Ff 
