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 loseth that polarity in a few hours; which may arise for its being too short for its weight, or from its different temper of hardness or softness. A third piece I also send you, 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. Would some ingenious man pursue these experiments, perhaps we might have needles made of brass to act as strongly as steel ones do, which would have the advantage of being less liable to rust at sea than steel ones are. But my whole design was to shew, that brass is by no means a proper metal to make compass-boxes of, or to be employed in any instrument where magnetism is concerned. For as it is demonstrable, beyond all contradiction, that some brass is found endued with a power of attracting the magnetic needle; that other pieces are capable of receiving it either by accident or design, (let it be from its being mixed with iron, or any other cause whatever) brass must be a very improper metal for compass-boxes, as it may occasion many sad and fatal accidents. Norwich, Octob. 20th, 1758. 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. H. Baker. London, Nov. 15. 1759. CVII. _An Account of the_ Sea Polypus, _by Mr._ Henry Baker, _F.R.S._ _To the Right Honourable the_ EARL _of_ MACCLESFIELD, President _of the_ Royal Society. [Read Nov. 23, 1758.] My Lord, I now return the marine animal your Lordship did me the honour to recommend to my examination; which I find to be a species of one kind of the Sea Polypi, mentioned by naturalists; but I think not very accurately described. The kinds of Sea Polypi are understood to be, _First_, The Polypus, particularly so called, the Octopus, Preke, or Pour-contrel: to which kind our subject belongs. _Secondly_, The Sepia, or Cuttle-fish. _Thirdly_, The Loligo, or Calamary. And each of these has its different species and varieties[159]. The ancients add the Nautilus; and some sorts of Star-fish might perhaps be not improperly ranged among them. All of the first kind have eight arms, placed at equal distances round the head; below the arms are two eyes, and the body is short and thick.