368 Dr. Barry’s Recapitulation of his 
that of the polar decomposition of water. The electro-positive 
and electro-negative elements are yielded up on opposite faces of 
the film, and its interior undergoesincessant polar changes,—the 
oppositely electric particles sliding as it were on one another. 
21. Ina late Number of this Journal I have described the 
remarkable power of certain electro-negative gasesin operating 
the rapid detithonization of surfaces that have been changed 
by light. Since that paper was sent to England I perceive 
from the * Scientific Memoirs,” that Professor Moser has 
published results of a similar kind. The true explanation of 
them appears to me to be very different from that which he 
gives; for his idea of vapours containing latent rays of parti- 
cular orders of refrangibility or colour, rests on a very feeble 
analogy, and strikes me as entirely without support. 
22. The view which I have taken of these pheenomena, and. 
to which allusion was made in the paper referred to, can be 
easily understood from what has just been said. ‘The film, 
on a Daguerreotype plate, which has been disturbed by the 
tithonic rays but not yet mercurialized, is in a polar condition 
of force, its iodine is ready to unite with a new layer of silver 
behind, its silver is ready to be evolved in front. If it be exposed 
to mercurial vapours union at once takes place on that front 
face, and an amalgam is formed; if to the vapours of iodine 
or chlorine or bromine, an iodide, chloride or bromide of 
silver is formed. In an instant, its disturbing affinities being 
satisfied, the film reverts back to its former condition of equi- 
librium, and is precisely in the condition it was in before ex- 
posure to the light. 
University, New York, March 7, 1843. 
LXIII. Facts relating to the Corpuscles of Mammiferous 
Blood, communicated to the Royal Society. By Martin 
Barry, M.D., F.R.SS. L. and E.* 
O observer can learn the structure of the blood-corpuscles, 
who does not carefully investigate their mode of origin, 
and patiently follow them through all their changes. Where 
are these changes to be seen? Not in blood taken from large 
vessels, which are merely channels for conveying it, but in that 
contained, and almost at rest, in the capillaries,—and especially 
in the capillary plexuses and dilatations; a remark which I 
believe is new, though many figures published by myself in 
the Philosophical ‘Transactions show the observations on 
which it is grounded to have been long since made. But 
there is another source from which my information has been 
* Communicated by the Author. 
