Colour and the Magnetic Properties of Bodies. 47 



also produce para-cyanogen, and proto-carburet of nitrogen, two sub- 

 stances of a dark colour, which, on the torsion balance, are feebly- 

 attracted by the magnet. 



CorolJ/B of Flowers. — The result of the trial of a number of dif- 

 ferent corollae on the torsion balance before a magnet, was, that the 

 white colours were, when fresh, diamagnetic, while the coloured 

 coroUse varied much, the diamagnetism of many being apparently 

 due to their moisture, which, at the same time, tends to make 

 them transparent ; moreover, I observed that change of season and of 

 the site of the flowering plant frequently had an influence. From 

 these experiments I may select one or two which serve to shew the 

 connection of colour with magnetic properties. Two cineraria flowers 

 were tried, the one white, tipped with crimson, the other a rich 

 strong blue; the white was inert, while the blue was decidedly at- 

 tracted. The corollae of the pile-wort and dandelion were compared 

 together, the first being attracted, the second repelled. The pile- 

 wort is an early spring flower, peculiar in its glistening surface, that 

 gives it a varnished appearance. Our fruit shops in the winter season 

 abound with dyed everlasting flowers imported from France, which 

 contain colours that shew very well the change of magnetic proper- 

 ties, and being in a dried state, the results are not subject to that 

 disturbance which the moisture of fresh flowers occasions ; the pale 

 yellow is diamagnetic, the dyed chrome-yellow nearly inert, the 

 verdigris-green feebly magnetic, and the logwood-purple magnetic. 

 I believe the effect of the sun's rays on the colours of plants has been 

 noted ; in the course of the above experiments I had to attend to 

 the nature of these changes. Solar rays bleach dead vegetable matter 

 with rapidity, while in living parts of plants their action is frequently 

 to strengthen the colour ; two opposite eff'ects, which, according to 

 my experiments, should be accompanied by diff*erent magnetic pro- 

 perties. The bleaching power of the sun's rays is familiar to every 

 one ; their power in developing fine colours is perhaps best seen on 

 the sides of peaches, apricots, apples, &c., &c., in these the sides ex- 

 posed to the midsummer sun being highly coloured. Durino- the last 

 open winter a wallflower plant aff'orded me the proof of a like effect ; 

 in the dark months there was a slow succession of one or two flowers, 

 to give it the appearance of flowering all the winter ; these were of a 

 uniform pale yellow hue ; in March streaks of a darker colour ap- 

 peared on the flowers, and continued slowly to increase, till, in April, 

 they were variegated brown and yellow, of rich strong colours. On 

 the supposition that these changes are accompanied by alterations of 

 magnetic properties, we may hereafter be able to explain Mrs Som- 

 merville's experiments on steel needles exposed to the sun's rays 

 under envelopes of silks of various colours. The results obtained by 

 that distinguished lady have been the source of much discussion among 

 men of science ; and there can be no doubt that the most rigid ex- 

 periments have failed to magnetize steel needles in the coloured rays 



