Professor Owen's Address. 3*79 



disc, in which time he found the spots passed through periodic 

 phases of increase aud decrease, the length of the period being 

 about eleven years. A comparison of the independent evidence 

 of the astronomer and magnetic period coincides both in its dura- 

 tion and in its epochs of maximum and minimum with the same 

 period observed in the solar spots. 



A few weeks ago, during a visit of inspection to our establish- 

 ment at Kew, I observed the successful operation of the photo- 

 heliographic apparatus in depicting the solar spots as they then 

 appeared. The continued regular record of the macular state of 

 the sun's surface, with the concurrent magnetic observations now 

 established over may distant points of the earth's surface, will ere 

 long establish the full significance and value of the remarkable, 

 and, in reference to the observers, undesigned, coincidence above 

 mentioned. Not to trespass on your patience by tracing the 

 progress of Magnetism from Gilbert to Oersted, I cannot but advert 

 to the time, 1807, when the latter tried to discover whether elec- 

 tricity in its most latent state had any effect on the magnet, and 

 to his great result, in 1820, that the conducting wire of a voltaic 

 circuit acts upon a magnetic needle, so that the latter tends to 

 place itself at right angles to the wire. Ampere, moreover, suc- 

 ceeded, by means of a delicate apparatus, in demonstrating that 

 the voltaic wire was affected by the action of the earth itself as a 

 magnet. In short, the generalization was established, and with a 

 rapidity unexampled, regard being had to its greatness, that 

 magnetism and electricity are but different effects of one common 

 cause. This has proved the first step to still grander abstractions, 

 — to that which conceives the reduction of all the species of im- 

 ponderable fluids of the chemistry of our student days, together 

 with gravitation, chemicity, and neuricity, to interchangeable 

 modes of action of one and the same all-pervading life-essence. 

 Galvani arranged the parts of a recently-mutilated frog so as to 

 bring a nerve in contact with the external surface of a muscle, 

 when a contraction of the muscle ensued. In this suggestive 

 experiment the Italian philosopher, who thereby initiated the 

 inductive inquiry into the relation of nerve force to electric force, 

 concluded that the contraction was a necessary consequence of the 

 passages of electricity from one surface to the other by means of 

 the nerve. He supposed that the electricity was secreted by the 

 brain,, and transmitted by the nerves to different parts of the body, 

 the muscles serving as reservoirs of the electricity. Volta made 



