[ l 92 ] 
at all, petrified or faturated with extraneous particles ; 
I would therefore propofe, not only that this N° 2. 
fliould be further calcined, in order to be fatisfied, 
whether it will, by that means, come to be of the 
fame nature with N° 1. but likewife that the follow- 
ing N° 3, 4, and 5. which Mr. Hubner fuppofes to 
be lefs calcined, fliould undergo the fame trial, in 
order to obferve, whether they will by that means 
become Tripoli 5 alfo to know, whether by being cal- 
cined for fome time (before they are reduced to tri- 
poli) they will put on the appearance of a coal like 
N° 2. for, if they do not, as I fufpeCt may be the 
cafe, it will be little lefs than a proof, that N° 2. 
which feems the plained; wood of any, differs from 
the others more eifentially than merely in its degree 
of calcination. Perhaps it may alfo be found, that 
N° 5,4, and y. differ not only from N° 2. but like- 
wife from N c 1. and may not be capable of being 
reduced to Tripoli. 
Remarks o?i the preceding Paper : In a 
Letter to the Right Honourable the Lari 
of Macclesfield, Pref. R. S. from Mr . 
Emanuel Mendes da Cofta, F. R. S . 
My Lord, 
Read June 2i, xy OUR Lordfliip’s commands to wait 
l 759 - X on Mr. Profeffor Hubner, when in 
England, to receive his paper on the production of 
Tripoli, which he defigned for the Royal Society, and 
to difcourfe with him thereon, in order to tranflate it, 
and 
