UPON GASES AND LIQUIDS. 575 



some globules of starch from a recently-cut potato, in a little 

 water on mica upon one of the angles of the parallelopipedal 

 halves of the keeper; simultaneously with the water, they were 

 repelled and di'iven outwards between the angles of the poles. 

 But when placed in a dilute solution of the protosulphate of iron, 

 instead of water, they were at first forcibly attracted towards the 

 middle of the upper angles simultaneously with the liquid ; but 

 when the liquid had acquired a state of rest, they resumed their 

 independent motion, and were repelled outwards by the poles. . 



54. The first paragraph in the preceding memoir had already 

 been despatched, before I had obtained the slightest knowledge 

 of Faraday's last paper upon the diamagnetism of gases. The 

 mere communication of the statement that No. 732 of the Journal 

 Vlnstitut contained a report of this paper induced me to hasten 

 in despatching this first pai'agraph, which, although it had 

 long been completed, had been intentionally kept back, to await 

 the result of two experiments, one of which merely consists 

 in a repetition of one of the experiments discussed in the pre- 

 ceding paragraphs ; and the other, which had been designed at 

 the very commencement of my experiments upon the diamag- 

 netism of gases, was obliged to be postponed for want of sun- 

 shine to the time when I should be able to institute my ex- 

 periments. The last experiment certainly now loses the interest 

 of novelty in consequence of Faraday's communication ; how- 

 ever I shall detail it in these supplemental investigations, although 

 still in an imperfect state, because it serves to complete the 

 series of experiments which I have described in the earlier 

 paragraphs. 



55. To begin with the first of the two experiments mentioned 

 in the preceding paragraph, it is a matter of daily experience 

 that when the sun shines upon a hot stove, the ascending air, 

 and upon an adjacent wall its shadow, are very distinctly seen. 

 This then was a means of rendering ascending heated air visible, 

 and thus of deciding whether heated air is more diamagnetic 

 than cold air, which, judging from the experiment upon flame, 

 I considered as probable (14), although I could not form any 

 opinion as to the demonstrabihty of the point by experiment. I 

 therefore placed a spiral of thin platinum wire, somewhat curved 

 toward the top, and with its long axis equatorial beneath the 

 approximated apices of the poles of the electro-magnet. When 



