Intelligence and Miscellaneous Articles. 95k 
imparted to the silver-salt is identical with that of the dye used; and, 
as has been shown above, that by no means follows. He supposed 
that the capacity of any given colour to influence the silver-salt 
depended upon its tendency to combine with Cl, Br, and I; 
whereas, as we have above seen, its action most probably depends 
upon its ability or inability to combine with the silver haloid. 
But the principal source of error has arisen from the fact that 
when the film is stained, the effect is necessarily a confused one. 
Besides any influence that may be exerted on the particles of silver 
haloid, these particles are virtually behind a colour-screen, which 
must materially modify the nature of the light that reaches them, 
and the final effect must necessarily be a combination from two 
distinct causes. Moreover, the colour in the film tends to arrest 
precisely those rays to which it is proposed to render the silver-salt 
more sensitive ; a consideration of the utmost importance, for the 
one action tends to counteract the other, and thus leads to inex- 
tricable confusion. From a system of experiments so faulty no 
just conclusions could be drawn. 
Whether, with these sources of error eliminated, Draper’s view, 
that a sensitive substance is influenced by those rays which it ab- 
sorbs, can be applied to these new combinations which I have here 
described, is a matter on which I am not prepared to express an 
opinion, haying been, much to my regret, unable as yet to examine 
the question. It seems @ przorz probable; but in that case it is impor- 
tant to observe that the effect will depend, jirsily, wpon the capacity 
of the dye to combine with the silver halou, and, secondly, not on the 
proper colour of the dye «isolated, but on the colour that the silver 
halowd acquires under its action, which, as we have already seen, 
may be something quite different from the colour of theoriginal dye. 
I have observed that the silver-salts are greatly changed by con- 
version into lakes, even when the colour imparted is but faint. 
They become in some cases much more finely divided and remain 
long in suspension. In one case at least a great increase of sensi- 
tiveness to light for development was observed. Later I shall 
hope to give more definite details on these points. 
In the above facts will doubtless be found an explanation of 
many of the anomalies in the behaviour of coloured films which 
have caused such wide differences of opinion. And the new modes 
of operating deducible from the reactions here described will, I 
think, be found of extended utility. Silver-salts can be dyed first 
and emulsified afterwards; and the ability to colour the sensitive 
salt to any shade with certainty, and without introducing a counter- 
acting influence into the film, gives a new power in photochemistry. 
—Silliman’s American Journal, January 1885. 
ON A SELENIUM-ACTINOMETER. BY M. H. MORIZE, 
OF RIO JANEIRO. 
The object of this instrument is to measure the relative inten- 
sities of solar luminous rays at different heights on the horizon. 
