358 Acknowledgements to Mr. Westgarth Forster 
by the breathing of animals ; but whether they are able, during 
sunshine, to reconvert into oxygen the carbonic acid they form 
during darkness aud common day-light.” 
The solution of this question I have attempted, and I hope 
one day to give a satisfactory answer to it. 
And, sir, [ presume I may also add that I have attempted a 
solution of the above question, particularly in the third and fourth 
experiment, as related in my first paper, in which the plants, 
inclosed in receivers, were exposed not to air vitiated by the 
breathing of animals ; but to common air, during darkness, com- 
mon day-light, and sunshine ; the former of the above for seven 
successive days, and the latter for there successive days, in both 
of which experiments it did not appear to me that the plants 
had the power during sunshine to reconvert into oxygen the 
carbonic acid they formed during darkness and common day- 
light. 
From these observations it appears that the subject is yet a 
controverted one, and that there are celebrated authors of the 
present day whose opinions are at variance with each other ; and 
I think it is meritorious in any one, ainid this conflict of cou- 
tending opinions, to communicate his researches to the common 
stock ; and most certainly [ anxiously wait the coming day on 
which W.H. G. has promised to give to the public the results of 
his critical experiments. But should he be inclined to make any 
further remarks on me, and expect an answer, he will please ta 
conclude with his real name and address. 
I am, sir, yours &e. 
Dorset-street, Oct. 20, 1817. J. TaTuM. 
P.S. Since I last addressed you, I have found that the small 
pustules on the ice-plant contain a very considerable portion 
of muriatic acid ; but the smallness of the quantity of the fluid 
which they contain has as yet prevented me from ascertaining 
with what it is combined. I am not aware that any one has 
hitherto noticed it. 
LVII. Acknowledgements to Mr, WxestGartu Forster; further 
Geological Queries, on the Basaltic Strata vf Durham and 
Northumberland ; and Suggestions regarding the Situation 
of the Granite Patches of the North of England, in its Series, 
of Strata, By A CorresponDENt. 
Fo Mr. Tilloch. 
Sir, — I BEG to return my best thanks to Mr. Westgarth For- 
ster, for the answers which he has afforded in your last number, 
page 216, to my 2d Question, as to the true character and position 
of 
