504 Prof. Roscoe on the Influence of Light upon Chlorine. 
distance more than half a mile from the point whence the sketch 
is taken. It is true that something of the structure observed by 
Mr. Huxley may be traced for some distance along the side of 
the glacier above the great moraine; but neither on the Brenva, 
nor on any other glacier, have I ever seen anything like a system 
of continuous lines or streaks distinctly visible at a distance, and 
over a wide breadth of glacier, as represented in this illustration. 
One word more as to the so-called lenticular structure. When 
Mr. Huxley speaks of veins of ice 9 or 10 inches in thickness 
and apparently lenticular, which I suppose means that the exposed 
section thins out on either side, I venture to question whether 
such veins form any part of the real veined structure, and whether 
they are not instances of what is by no means rare,—the filling- 
up of small crevasses with ice generally differing im colour and 
appearance from the surrounding mass. I do not recollect to 
have attended to the length of the veins, or the exposed sections 
of them on the glacier of the Brenva, but I can only say that if 
9 feet be the greatest length that can there be traced, the struc- 
ture of that glacier must differ from all those of the same class 
that I have ever been able to examine. 
LVII. On the Influence of Light upon Chlorine. 
By Prot. H. E. Roscoz, Ph.D. §e. 
To the Editors of the Philosophical Magazine and Journal. 
Owens College, Manchester, 
GENTLEMEN, November 1857. 
iT WISH to make a few observations upon a communication of 
Dr. Draper’s, published in the last (November) Number of 
the Philosophical Magazine, in which he refers to the researches 
on the chemical action of light, recently published by Professor 
Bunsen and myself, in a manner calculated to mislead many of 
your readers as to the results we obtaimed, and the conclusions 
which must follow therefrom. 
In 1843, Dr. Draper observed that when a mixture of chlorine 
and hydrogen is exposed to light from various sources, a certain 
time elapses before combination begins, and that, when com- 
menced, the action continually increases, until at length a perma- 
nently constant maximum has arrived. In our experiments 
we have obsetved the same fact, and haye devoted one complete 
section of our research to the minute consideration of these re- 
markable relations. We differ widely, however, from Dr. Draper 
as to the cause of this phenomenon ; and it is the experimental 
evidence upon which we rest our explanation which I think it 
advisable here briefly to state. 
