MECHANICS AND USEFUL ARTS. 23 



formed an important step, which led to a brilliant series of experiments 

 and discoveries, with inventions, such as the Leyden jar, for intensifying 

 the electric shock. The discovery of the instantaneous transmission of 

 electricity through an extent of not less than 12,000 feet, by Bishop "Watson, 

 together with that of the electric state of the clouds, and of the power of 

 drawing off such electricity by pointed bodies, as shown by Franklin, 

 were a brilliant beginning of the application of the science to the well- 

 being and needs of mankind. Magnetism has been studied with two 

 aims : the one, to note the numerical relations of its activity to time and 

 space, both in respect of its direction and intensity; the other, to penetrate 

 the mystery of the nature of the magnetic force. In reference to the first 

 aim, my predecessor adverted, last year, to the fact, that it was in the com- 

 mittee-rooms of the British Association that the first step was taken towai-ds 

 that great magnetic organization which has since borne so much fruit. 

 Thereby it has been determined that there are periodical changes of the 

 magnetic elements depending on the hour of the day, the season of the 

 year, and on what seemed strange intervals of about eleven years. Also, 

 that, besides these regular changes, there were others of a more abrupt and 

 seemingly irregular character Humboldt's "magnetic storms" which 

 occur simultaneously at distant parts of the earth's surface. Major-General 

 Sabine, than whom no individual has done more in this field of research 

 since Halley first attempted " to explain the change in the variation of the 

 magnetic needle," has proved that the magnetic storms observed diurnal, 

 annual, and undecennial periods. But with what phase or phenomenon of 

 earthly or heavenly bodies, it may be asked, has the magnetic period of 

 eleven years to do ? The coincidence which points to, if it does not give, 

 the answer, is one of the most remarkable, unexpected, and encouraging, to 

 patient observers. For thirty years a German astronomer, Schwabe, had set 

 himself the task of daily observing and recording the appearance of the 

 sun's disc, in which time he found the spots passed through periodic phases 

 of increase and decrease, the length of the period being about eleven years. 

 A comparison of the independent evidence of the astronomer and magnetic 

 observer has shown that the undecennial magnetic period coincides, both in 

 its duration 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 establishment 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 mag- 

 netic observations now established over many distant points of the earth's 

 surface, will, ere long, establish the full significance and value of the re- 

 markable, 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 electricity in its most latent state 

 had any effect on the magnet, and to his great result, in 1820, that the con- 

 ducting 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, 

 succeeded, by means of a delicate apparatus, in demonstrating that the vol- 

 taic 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 



