330 Galvano-Magnetic Apparatus of Prof. Dana. 
-] visited him soon after the shock, and witnessed the de-. 
molishing effects of the lightning. The place where it 
struck is a projection of one story, at right-angles with the 
house, which is two stories high, and within a few feet of 
their junction. Mr. R. wasin the house at the time. It 
was rather difficult to decide whether the lightning ascend- 
where the first vestiges of the lightning were perceivable, 
was directly under the branches, and but three feet from 
the trunk of a lofty poplar, which remained unburt—thus 
affording an additional proof to what is stated in your No. 
for June last, that this tree isa poor conductor and no 
safe-guard against lightning. I would remark also, that 
there was'a good rod to the house, sixty-three feet distant 
\ 
from the smitten. spot. 
ArT. XV.—Galvano-Magnetic Apparatus of Prof. Dana. 
(See Figure 6 in Plate 12 at the end.) 
N S soon arranges itself in the plane of the magnetic meri- 
dian; the steel wire becomes a temporary magnet, and will 
