Magnetic Influence of Solar Light. 371 



To this I reply they are identical, for as the exposed extre- 

 mity of needle A during the period of action pointed to the 

 south pole of the earth, the force of induction would tend to 

 generate in that extremity a northern Polarity, and such 

 Polarity really exists in it, although in a former paragraph 

 I stated it had become a south pole. The form of expression 

 to which allusion was made in the first section of these 

 experiments, immediately explains this apparent anomaly, 

 since it was then stated that while, by sanction of custom, 

 the extremities of a magnetic needle that point to the north 

 and south poles of the earth, are called respectively the 

 north and south poles of the magnet, the nature of the 

 Polarities resident in them is precisely the converse of that 

 indicated by the terms employed. Now it has often been 

 experimentally proved that the inductive action of the earth's 

 magnetism will act upon very small masses of steel or iron, 

 changing the one permanently, the other temporarily into 

 magnets, and hence I conclude that experiments on the sub- 

 ject of Solar magnetism, from which reference to it has 

 been excluded, are seriously deteriorated, if not rendered 

 wholly valueless. That such a cause may have interfered 

 with Mrs. Somerville's results I cannot doubt, when I find 

 the needles in her experiments were suspended vertically, thus 

 being only about 20° removed from the line of dip, which in 

 the latitude of London is about 70°. In farther confirma- 

 tion of this view, I may mention that Faraday has repeatedly 

 employed the vertical as a sufficiently close approximation 

 to the actual dip, throughout the course of his beautiful 

 experiments on Terrestrial magneto-electric induction, and 

 has exhibited perfectly decisive and satisfactory results with 

 it, and apparatus of a very minute character. 



Exp. II. Experimental needle B, having a length of 1.5 

 " and a diameter of 0.016," prepared similarly to the pre- 

 ceding, was exposed under a dark green glass from | p. m, 

 to If p. m. and on being tested exhibited the following 



