286 PHILOSOPHICAL TRANSACTIONS. [aNNO 1758. 



yet like natural magnets, in contact, or nearly so, they attract each other : there- 

 fore when you would show the repelling power of this brass bar, you must not 

 bring it nearer the needle than -^ of an inch. Magnetic brass does not attract 

 iron, not even the least particle, as far as I can find : whether this is owing to 

 the weakness of magnetism in the brass, or to some other cause, I do not pre- 

 tend to know. 



I have tried to infuse magnetic virtue in several pieces of copper, lead and 

 pewter; but all my endeavours have not been able to make them attract the 

 needle at all. Indeed, when I have held a piece of pewter that I have tried to 

 make magnetical to the needle, the needle would tremble, but not approach the 

 pewter. I send you another piece of brass, whose either end attracts either of 

 the poles ; this I have infused the magnetic virtue into, and can at any time, so 

 as to attract and repel the needle ; but, like steel that is set a low blue, it loses 

 that polarity in a few hours; which may arise from its being too short for its 

 weight, or from its different temper of hardness or softness. A third piece I 

 also send, which with all my endeavours I cannot make attract the needle in the 

 least ; and yet I can perceive no difference between the appearance of this piece 

 and that of those which do. 



It is well known, that brass has been sometimes found to affect and disturb 

 the magnetic needle ; but to give magnetism and polarity to brass, has not, that 

 I have yet heard, been before attempted. I therefore have taken the liberty to 

 lay the above account before this Royal Society, and have also brought the pieces 

 of brass mentioned therein, which have been thus made magnetical. 



Cni' Of the Sea Polypus* By Mr. H. Baker, F. R. S. p. 777. 



The kinds of sea polypi are understood to be — 1st, The polypus, particularly 

 so called, the octopus, preke, or pour-con trel : to which kind the present subject 

 belongs. 2dly, The sepia, or cuttle-fish. 3dly, The loligo, or calamary. And 

 each of these has its different species and varieties.-|~ The ancients add the nau- 

 tilus ; and some sorts of star-fish might perhaps be not improperly ranged among 

 them. 



All of the fir^t kind have 8 arms, placed at equal distances round the head ; 

 below the arms are 2 eyes, and the body is short and thick. The cuttle-fish 

 and the calamary have each of them 10 arms; of which 8 are shorter ones, ta- 

 pering gradually to a point from the head, where they all rise to their extremities: 

 the other 2 (frequently called tentacula) are 3 or 4 times as long, perfectly round, 



* The species here described by Mr. Baker is the American cuttle-fish, and is not to be con- 

 founded with the common cuttle-fish or sepia octopodia of Linneus. It is figured in Seba's Thesau- 

 rus, vol. iii. pi. 1, fig. 2 and 3, from a much larger sjjecimen than the present. 



+ Vide WUkin's real Character, p. 131. Bellon. Aquat, p 330.— Orig. 



