1816.] Scientific Intelligence. 159 
the quantity of gas yielded by coals. I found that the tar could 
be almost completely converted into gas during the first distillation, 
by making the whole pass through a red-hot tube. I conceive this 
method might be economically adopted by the Coal Gas Company. 
They would probably be able by means of it to obtain by the first 
distillation double the quantity of gas which they procure at present, 
and thus save a considerable sum, which they must at present waste 
on a second distillation. 
III. Condensation of Water on Glass. By Dr. Wells. 
(To Dr. Thomson.) 
SIR, London, Jan. 5, 1816, 
I think it very probable that glass may attract moisture from the 
atmosphere through some special quality, originating, perhaps, in 
the alkali which forms a part of it, and that this cireumstance occa- 
sioned the plate of your electrical machine, as mentioned by you in 
the last number of your Journal, to be wet, while other bodies, 
though similarly situated, were dry. The quantity of moisture, 
however, which you found upon the plate, I would denominate 
simall, notwithstanding that it is called by yourself considerable. For 
you said, if I recollect rightly, when you related this circumstance 
to me in conversation several weeks ago, that the moisture on the 
plate was uniformly diffused over it, which appearance I regard as 
only the commencement of the formation of dew, agreeably to 
what I have remarked in the eighth page of my essay. I am of 
opinion, therefore, that although it should be established by fur- 
ther observations,‘ that glass can attract moisture from the atmos- 
phere, in some way unconnected with its greater cold, still the 
quantity hence arising will always be very trifling, when compared 
with what it receives in consequence of its lower temperature. 
Iam, Sir, your most obedient humble servant, 
Witiram Cyarces WELLS. 
IV. Royal Society. 
As the writer of the excellent letter which constitutes the first 
article of the present number does not appear to be sufficiently 
aware of the nature and constitution of the Royal Society, it may 
be proper to say a few words on the subject. The Royal Society 
consists of an association of Gentlemen for the express purpose of 
promoting the cultivation of the natural sciences. Theexpense of 
the association, which is considerable (for Government, so far from 
supporting the association, as is done in other countries, charges it 
with taxes which amount to several hundreds a year), is defrayed by 
the annual contributions of the members. This circumstance pre- 
vents the possibility of conferring the title of Fellow upon any 
person, however celebrated, unless he petition for it. Such a title 
would be, in fact, imposing on him a tax of 2/: 12s, a year, which 
the Royal Society has no right todo. Jf, therefore, the mathema- 
