OF THREE LAKGE LOADSTONES. 387 
It is a fact well known, that large masses of this mineral 
often have a weak power, and that small specimens gene- 
rally have a stronger proportional energy. We have an 
example of this in the account given of the large specimen 
in the Leverean Museum, which is stated to have a very 
weak power; and the three small specimens noticed by 
Mr Martin, which presented a very great power. One 
of these belonged to Mr Haac ; it weighed 14| ounces 
when armed, and carried 16 times its own weight. Another 
belonged to the Honourable Mr Berkeley, then at Bru- 
ton ; it weighed 43 grains when armed, and carried 1032 
grains, being 24 times its own weight. And the third, 
which Mr Newton wore in a ring, weighed scarce 3 grains, 
it took up 746 grains, being 250 times its own weight. (See 
Plate XII. fig. 1.) In these three small specimens we find 
the power of attraction to be comparatively gi'eatest the 
smaller their size is. Mr Newton's carried no less than 
250 times its weight, whereas Mr Berkeley's only carried 
24 times, and Mr Haac's only 16 times, their respective 
weights. 
Such being the general character of natural magnets, 
with regard to the comparative attractive power of small 
and large ones, it is of some importance to notice three 
large loadstones, which arrived here a few years ago, and 
were purchased by Mr Sanderson, lapidary in this city. 
These form an exception so far to the above conclusions. 
No public notice has yet been taken of these natural pro- 
ductions ; and as two of them remained for ten months in 
my possession, and presented several peculiarities, I now 
take the liberty to notice them to the Society. 
They are said to have been removed from Moscow, when 
the French were advancing towards that city, previous to 
its being burnt ; they were then conveyed to Petersburgh, 
and from thence shipped to this country. They were cased 
