and Remarks on the Theory of Magnetism, 19 



still water, indicate polarity, by pointing according to the mag- 

 netic meridian. Feathers, hair, and the pistils of large plants, 

 as the digitalis and antirrhinum, appeared to me, when treated 

 in the same way as the needles, to indicate a similar disposition. 

 If the downy part of feathers, fine hair, or the large thistle 

 down, is laid upon an electric, after friction, the parts that pro- 

 ject beyond the sides of the electric, are considerably attracted 

 by the magnet. 



All electrics evince polarity, and those that have the power 

 of retaining electricity long, demonstrate this, by pointing north 

 and south, if formed into an oblong, and made to swim by 

 means of a thin piece of cork on water, after being excited to 

 an electrical state by friction. The tourmaline, ruby and brazU 

 iian topaz readily exhibit this. 



The affinity of iron to all the imponderable substances seems 

 greater than that of any other body, electricity, galvanism, heat 

 produced by percussion, and coloured light) rendering the iron 

 magnetic ; and the magnetic property, when once acquired, con- 

 veying such a sensibility to the metal, to all the impulses of 

 these bodies, that I found, when a number of small needles were 

 rendered magnetic, and so placed as to traverse freely, being 

 connected together at small distances by any light substance, 

 and so arranged in reference to each other, that none of the 

 needles could shew its tendency to the poles of the earth ; they 

 then indicated, by their motion^ the impressions they received 

 from the sun's rays, the radiation of caloric, and the other sub^ 

 tie bodies alluded to ; but this will be easier apprehended by 

 stating the following experiments. 



Twfelve or fifteen needles (of the size marked No. 10, used 

 for sewing) were rendered magnetic, and stuck into a thin cir- 

 cular slice of cork, of an inch diameter, at the distance of one- 

 sixth of an inch from each other. The heads of the needles were 

 so* fixed into the piece of cork, that they stood perpendicularly ; 

 and all the points being south poles, stood uppermost. The 

 cork was then placed on the centre of a surface of water, 1^ feet 

 in diameter. The needles, in this situation, being prevented 

 from evincing any polar attraction by their perpendicular posi* 

 tion, were attracted by a moderate degree of light, heat, or elec- 

 tricity, but were repelled by the more powerful impulses im-^ 



B 2 



