.182 Electricity of Nature, 



1. The sun is the source of ligJit^ which is imparted to the 

 earth in beams or rays. This solar light is the origin of the 

 colouring principle throughout nature. The fact is proved 

 by daily observation upon the effects produced by light upon 

 vegetable bodies, and by numberless chemical and prismatic 

 phenomena. Magnetic properties are communicated by the 

 blue and violet rays. This was noticed by Dr. Morichini of 

 Rome ; and the fact, as is familiarly known, was established 

 by the experiments of Mrs. Somerville ; who covered one half 

 of a sewing-needle with paper, and exposed the other half, for 

 two hours, to the violet rays, by which the needle acquired 

 polarity. 



2. Heat is generated by the rays, and is particularly mani- 

 fested in those rays that are most remote from the others 

 that evince magnetic powers. Thus, the heating power in- 

 creases from the middle of the prismatic spectrum to the red 

 ray, and is greatest beyond the visible boundary of that ray. 

 These facts were ascertained by Dr. Herschel, and confirmed 

 by Sir H. Englefield and Sir Humphry Davy. 



3. The sun's rays, it should appear, are not the direct 

 vehicles of heat; for not only does the temperature of the 

 transparent media through which they pass remain unaltered, 

 but that of the atmosphere is subject to sudden and various 

 mutations, without any assignable cause. The last-named 

 fact may be within the recollection of almost every attentive 

 observer of the weather ; because he must have remarked 

 that, in one and the same day, perhaps within the space of 

 an hour, there has been an increase or reduction of thermo- 

 metric temperature of from 5° to 10°, without any sensible 

 alteration in the power and brilliancy of the sun's rays. 



4. Electricitij is originated and made manifest by the solar 

 agency. This, perhaps, may be considered a self-evident 

 fact, and one proved by the frequent occurrence of thunder 

 storms, and of silent evening lightning during very hot wea- 

 ther. These phenomena, however, I cannot consider as 

 affording, by any means, the most conclusive evidence of the 

 electrising agency of the solar rays ; for they admit of several 

 marked exceptions. In the second and fourth leading sec- 

 tions of February and April, in the Domestic Gardener'' s 

 Manual, I have endeavoured to point out many striking phe- 

 nomena, which can scarcely fail to indicate the direct elec 

 trical agency of the sun ; but these my limits will not now 

 permit me to adduce. I shall content myself by observing, 

 that if (as was stated by Mr. Ritchie, in the lecture before 

 alluded to) the sun may be regarded as " the visible cause of 

 terrestrial magnetism," a phenomenon which, perhaps, may 



