442 PROCEEDINGS OF 



needle to tho pole, is not a correct simile for the same place, anJ, if we pass from 

 one spot to another, is falsified at each change of our position ; for the needle 

 changes its direction, and the force varies. Enlarged and united observations, 

 embracing the various portions of the world, must produce important results. 

 The observations at Philadelphia, conducted by Dr. A. D. Bache, and now con- 

 tinued by him under the direction of tho Topographical Bureau, are of great value, 

 and will, it is hoped, be published by Congress. Part of them have already first 

 seen the light in Europe — a result much to be regretted, for we are not strong 

 enough in science to spare from the national records the contributions of our coun- 

 trymen . 



These combined observations, progressing throughout the world, are of the high- 

 est importance. The University of Cambridge, the American Philosophical Socie- 

 ty, and Girard College, have erected observatories ; and one connected with the 

 Depot of Charts and Instruments, has been built last year in this city by the Gov- 

 ernment, and thoroughly furnished with instruments for complete observations 

 The names of Bache, Maury, Gillis, Pierce, Levering, and Bond, are well known 

 in connection with these establishments. 



A magnetic survey of Pennsylvania has been made by private enterprise, and 

 the beginning of a survey in New York. Loomis has observed in Ohio, Locke in 

 Ohio and Iowa, and to him belongs the discovery of the position of the point of 

 greatest magnetic intensity in the Western World. Most interesting magnetic 

 observations (now in progress of publication by Congress) are the result of the 

 toilsome, perilous, and successful expedition, under Commander Wilkes, of our 

 navy, by whom was discovered tlie Antarctic continent, and a portion of its soil 

 and rock brought home to our country. 



The analogy of the auroral displays with those of electricity in motion, were 

 first pointed out by Dr. A. D. Bache, whose researches, in conjunction with Lloyd 

 of Dublin, to determine whether differences of longitude could bo measured by the 

 observations of small simultaneous changes in the position of the magnetic needle, 

 led to the knowledge of the curious fact, that these changes, which had been 

 traced as simultaneous, or nearly so, in the continent of Europe, did not so extend 

 across the Atlantic. 



Kindred to these two branches, are electro-magnetism and magneto-electricity, 

 connected with which, as discoverers, are our countrymen Dana, Green, Hare, 

 Henry, Page, Rogers, and Saxton. The reciprocal machine for producing shocks, 

 invented by Page, and tho powerful galvanic magnet of Henry, are entitled to re- 

 spectful notice. This force, it was thought, might be substituted for steam ; but 

 no experiments have as yet established its use, on any important scale, as a mo- 

 tive power. The fact that an electrical spark could bo produced by a peculiar ar- 

 rangement of a coil of wire, connected with a magnet, is a recent discovery ; and 

 tho first magneto-electric machine capable of keeping up a continuous current waa 

 invented by Saxton. 



Electricity and magnetism touch in some points upon heat. Heat produces electri- 

 cal currents; electrical currents produce heat. Heat destroys magnetism. Melted 

 iron is incapable of magnetic influence. Reduction of temperature in iron so far 

 decreases tho force, that a celebrated philosopher made an elaborate series of ex- 

 periments to ascertain whether a great reduction of tomporaturo might not developo 

 magnetic properties in metals other than iron. This branch of thermo-electricity 

 has received from us but little attention. Franklin's experiments, by placing dif- 



