VOL. L.] PHILOSOPHICAL TRANSACTIONS. 285 



followed by a violent purging ; both which continued for 4 hours, during which 

 it was thought he would die. At length these symptoms became less ; and the 

 negroes made him walk, and stir about by degrees; and soon after they were 

 stopped. Rice-gruel, which they gave him, put an end to all these disorders ; 

 and in 24 hours he had no more ailments nor pain ; the swelling of his belly 

 diminished in proportion to his evacuations upward and downward, and he had 

 continued his functions without being any more sensible of the poison. We see 

 by this that the effects of the poison of the manchinelle are different from those 

 of the fish at Guadaloupe. 



Cn. Abstract of a Letter from Mr. Wm. Arderon, F.R.S. to Mr. Henry 

 Baker, F. R. S. on giving Magnetism and Polarity to Brass, p. 774. 



Mr. A. having made experiments on the magnetism of brass, among many 

 pieces that he had tried, were several that readily attracted the needle ; but 

 whether they had this property originally, or received it by hammering, filing, 

 clipping, or any other such like cause, he could not determine. He had a very 

 handsome compass-box made of pure brass, as far as he could judge : the needle 

 being taken out, and placed on a pin fixed properly in a board, and clear of all 

 other magnetics, the box will attract this needle at half an inch distance ; and if 

 suffered to touch, will draw it full QO degrees from the north or south points ; 

 and he thought those parts of the box marked north and south attracted the 

 strongest. The cover of the box also attracted the needle nearly as much as the 

 box itself. 



As to your supposition, says Mr. A., that iron may be mixed with the brass, 

 I do not know; but I have been informed it cannot be, as brass fluxes with a 

 much less degree of heat than iron, and iron naturally swims on fluid brass. Be- 

 sides, many of the specimens of brass I have tried were new as they came from 

 the mill, where they were wrought into plates, and I presume were not mixed ;* 

 yet these I have given the magnetic virtue to when they had it not ; and some 

 pieces of brass, which naturally attract the needle, seem to the eye as fine a 

 bright yellow as any other, and are as malleable as any I ever met with. Pieces 

 of brass without any magnetic power, by properly hammering and giving them 

 the double touch, after Mr. Mitchel's method, I have made attract and repel the 

 needle, as a magnet does, having 2 regular poles. You will observe, when you 

 try this bar, that the same poles repel each other, and the contrary poles attract ; 

 which proves this piece of brass to be endued with true magnetic virtue and po- 

 larity. However it must be noted, that though the same poles repel each other 



* This refers to Mr. Baker's having supposed, that old iron and old brass nnay be mixed some- 

 times, and melted down together. — Orig. 



