238 Mr. Christie on magnetic 
wire so that they shall vibrate in the same time, I have in 
vain made almost daily attempts to obtain a complete set of 
observations. The observations however which I have given 
are, I think, quite conclusive as to the fact of the compound 
solar rays being possessed of magnetic properties. 
As we can scarcely suppose that the terminal excess in the 
case of the glass needle is due to magnetism in the glass, 
deducting this portion from the terminal excess with the 
other needles, the ratio of this excess with the magnetised 
needle to that with the copper needle would be 17 to 1, a 
result not very improbable, though the small difference in 
this excess with the copper and glass needles may very pos- 
sibly have arisen from other causes. But if the effect with 
the glass needle cannot be attributed to magnetic influence 
any how exerted, what cause are we to assign for it ? It is 
possible that the terminal excess in this case may have arisen 
from currents of air excited within the box by the rays of 
the sun : or probably electricity is excited in the glass needle 
on exposure to the rays of the sun, and the box becoming 
electric by induction, a drag between the needle and the box 
causes a diminution in the arc of vibration. The latter sup- 
position would accord with the recent highly interesting ex- 
periments of Mr. Babbage. I am not aware that such effects 
as these have ever before been observed during vibration, 
and there certainly appears great difficulty in assigning any 
cause for them : however, until further observations may 
have thrown greater light on the subject, we must be satis- 
fied with having ascertained the facts. 
I have not as yet made any observations to ascertain what 
may be the effects when a needle vibrates exposed to the 
