H, A. Rowland—Diamagnetic Attachment to the Lantern. 357 
To the red rays, including those whose wave-lengths are 
from 1605 to the end of the visible spectrum, coralline very 
ge saelonalsbl the sensitiveness of AgBr. 
To t ellow rays, taking as representatives those whose 
wave- leigh s vary only moderately from 4570, coralline moder- 
ately increases the sensitiveness of AgBr. 
To the green rays, es. principally those whose wave- 
lengths lie” between 517 and 569, coralline gives no increase 
whatever of sensitiveness to AgBr. 
So that coralline, far from being a = . Pe theory of 
Dr. Vogel, gives in fact a confirmation of my own view, viz: 
that substances heighten the sensitiveness of AgBr to particular 
rays, without the existence of any relation between the color 
of that ray and their own proper color 
It is a little curious that coralline acts very differently with 
AgI. So far from increasing the sensitiveness of that substance 
to red light, it actually diminishes it. 
Rosaniline is another substance whose action conflicts with 
Dr. Vogel's law. I find that it quite destroys the sensitiveness 
of AgBr to yellow rays. 
From all the foregoing I conclude, that there exists no rela- 
tion whatever between the color of substances and the color of 
the ray to A influence they modify the sensitiveness of 
silver ‘es 
faivanetyeny sak 20, 1875. 
Art. XXXVIIL—On a New Diamagnetic Attachment to the 
Lantern, with a Note on My Theory of the ay engi KE In- 
ductively Magnetized Bodies; by Henry A. RowLaNnD, As- 
ieidg Professor of Phys in the Rensselaer Patptestnie 
nstitu 
- seers of Apparatus. 
ny I place in my lantern and magnify to a loos size on 
e scre 
The effects obtained in this way are very fine and are not 
surpassed by those with the largest magnets; and we are by no 
means confined to strongly diamagnetic substances, but, with 
proper care, can use anything, even the most feeble. The appa- 
