Mrs. M. Somerville on the magnetizing power, &c. 133 
netised, and run through a small piece of cork, into which a 
conical cap of glass is inserted ; the whole traverses on the 
point of a needle fixed perpendicularly in a stand. 
I had no information at this time of the manner in which 
Professor Morichini had conducted his experiments ; but it 
occurred to me that it was not likely that if the whole of the 
needle were equally exposed to the violet rays, the same 
influence should, at the same time, produce a south pole at 
one end of it, and a north pole at the other. I therefore 
covered half of the needle with paper, and fixed it to the 
panel with wax, between ten and eleven in the morning, in 
such a position that the uncovered part of it should be exposed 
to the violet rays. The needle was placed in a vertical plane, 
nearly perpendicular to the magnetic meridian, and inclined 
to the horizon. As I had not a heliostat, it was neces- 
sary to move the needle in a direction parallel to itself, to 
keep the exposed portion of it constantly in the violet ray. 
The sun was bright at the time, and in less than two hours 
I had the gratification to find that the end of the needle 
which had been exposed to the violet rays attracted the 
south pole of the magnetic needle, and repelled the north 
pole. It had been previously ascertained that there was no 
iron near to disturb the results. The experiment was also 
repeated on the same day, under precisely similar circum- 
stances, with the view of detecting any source of error that 
might have escaped observation in a first attempt ; but the 
result was the same as in the first. 
The season was so favourable that it afforded me daily 
opportunity of repeating the experiments, varying the size 
of the needles, always taking especial care to ascertain that 
