_ 208 Remarks on 
Animals, in which he faithfully notices all that had been done by 
his predecessors, and establishes the point by abundant research, 
that the whole of animated nature, whether vegetable or animal, 
abstracts the oxygen of the air, which is entirely bestowed in the 
production of carbonic acid. In Mr. Ellis’s second volume (a 
most elaborate and interesting performance, and the latest work 
on the subject,) Mr. Tatum will find the question resumed ; and 
that while Mr. Ellis maintains that carbonic acid is the result of 
the natural respiration of plants, he proves that there isa second 
function, by which, during bright sunshine, the carbonic acid so 
formed is reconverted into oxygen. This process, he contends, 
is entirely a chemical one, depending on the chemical agency of 
light, and by no means to be considered as a necessary or na~ 
tural operation. Thus far and much other interesting matter, 
with regard to the difference of colour in different plants and at 
different times of the year, Mr. Ellis has ably established. The 
question still remaining is, not whether plants have the power of 
counteracting the vitiation produced by the breathing of animals; 
but whether they are ableduring sunshine to reconvert into oxygen 
the carbonic acid they form during darkness and common day- 
light. The solution of this question I have attempted, and I 
hope one day to give a satisfactory answer to it. The sixth 
author who has touched on this question is Sir H. Davy, in his 
Agricultural Chemistry, who details two experiments which he 
made in order to convince himself that Mr. Ellis had not been 
deceived by his extensive researches. 
Independently of these works Mr. Tatum will find an analysis 
and critique of Mr. Ellis’s opinion in the Quarterly Review; and 
the subject is also fully discussed in Murray’s and Thomson’s 
Systems of Chemistry. JT conclude by saying, that all Mr. T’s 
experiments have been executed before, and some of them a 
dozen times over, 
I am, sir, Yours respectfully, 
W.H. G. 
XXXII. Remarks on Sir R. Purirps’s Defence of his Hypo- 
thests. By Mr. Tuomas TrEpDGoLp. 
To Mr. Tilloch. 
Si, — As Sir R. Phillips has favoured some of my remarks on 
his hypothesis with a reply, I will endeavour once more to con- 
vince him of the fallacy of the opinions he has put forth. 
Sir Richard appeals to experience, without once bringing for- 
ward an experiment to prove the correctness of his views ; and 
to the laws of Newton and of Nature, without once showing that 
they 
