400 PHILOSOPHICAL TRANSACTIONS. [aNNO 1730. 



low the substance of the tail, and were edged with thick and long hair, and 

 terminated broad, as in females. On the left side, these plates were much less 

 extended below the tail ; were almost totally void of hair, and terminated in 

 acute angles. These plates diverged likewise on the right side, as in the fe- 

 males, but not on the left side, as in the males. 



On removing part of the great shell, Dr. N. found the internal parts of gene- 

 ration in both sexes exactly corresponding to those externally described. In 

 the right side, adjacent to the heart, the oviduct was regularly disposed, it was 

 full of ova, and sent off its oviduct or uterus, to the antepenultimate leg. In 

 the left side, the testicle was rightly disposed as to its form, substance, and 

 situation ; part of which he was obliged to remove, to show the penis, which 

 terminated as in all males, at the tubercle in the lirst joint of the last leg, 



Magnetical Observations and Expe7-i?ne7its. By ServingtoJi Save?y, Esq. of 

 Shilston. N''414, p. 295. 



Precognita. — 1 . What Mr. Savery calls the magnetical line, is the position of 

 a dipping-needle when it ceases from oscillating, and is at rest in the magnetical 

 meridian of the place. 



2. By the word magnet, he means not a loadstone only, but either that, or 

 iron or steel, when they have permanent polarity, or any thing else having a 

 sensible magnetical or polar attraction. 



3. Of the magnetical needle, he calls that the north end which, if hung 

 horizontally, naturally turns, to the north, and that the south end which turns 

 to the south : but when using the words pole of a needle, he calls that the 

 north pole which turns to the south, and that the south pole which turns to 

 the north, 



4. Of touched iron or steel, as well as of the loadstone itself, he calls that 

 the north pole which attracts the north end, i, e. the south pole of the needle, 

 and that the south pole which attracts the south end, or north pole of the 

 needle; or in other words, he calls that the north pole, in all sorts of magnets, 

 which is endued with the same kind of virtue with the north pole of the earth, 

 and consequently is repelled by it: e contra, &c. 



5. Mr. S. prepared nails of several sizes, from the smallest sort of bellows- 

 nails to the largest sort of rafter-nails, one or two of each sort, or more of the 

 smaller. He held each of them perpendicularly with its point upwards, and 

 placing on it the plain side of a file horizontally, he filed off a little from its 

 point, more or less, according to the size of the nail, perhaps about the thickness 

 of a sixpence from a sixpenny one. Then on a plain hone, held horizontally, 



