45T 
Natural Philosophy, — Electricity. 
supposed to be nearly half that of the large one : it measures 
in length 5| inches, in breadth 4, and in height about 8 inches. 
On the 27th November 1818, I had suspended from it a mass 
weighing 80 pounds, independent of the conducting iron. These 
two natural magnets were brought to this country in the same 
vessel : the corresponding poles of both had most probably been 
placed together, for when they arrived in Edinburgh, the weak- 
er loadstone had its poles changed. A curious fact, which I 
found exhibited by the largest of these two, deserves particular 
notice. The full F D 
south pole, and the force of south attraction ran along the line 
CD. 'J'he north pole, however, was quite correct, being most 
powerful at H, and along the line HG. This appearance may 
arise from one of three circumstances^ : 1st, A may be a mass of 
ironstone which is not magnetic : 2dly, It may be an ironstone 
paste, added to complete the shape of the loadstone ; or, Sdly, 
it may be a distinct magnet. If either of the two first sup- 
positions be true, then the power of the loadstone may not be 
injured by the presence of A ; but if the last be correct, then 
the power must be much weakened. From the external ap- 
pearance of the loadstone, on both sides of the line of extreme 
south attraction, I am rather inclined to think that this last is 
the most likely of the three. If we allow this to be the case, 
then, by removing A, we must greatly add to the quantity of 
magnetic effect displayed at the two poles.” 
ELECTRICITY. 
17. Excitement of Muscular Fibre by Voltaic Electricity . — 
The following observations on the subject have been communi- 
