76 cosmos. 



the alterations of declination (see Lamont in Poggend., Ann. 

 der Phys., 1851, bd. 84, s. 572-582 ; and Relshuber, 1852, 

 bd. 85, s. 179-184). The already-indicated conjectural con- 

 nection between the periodical increase and decrease in the 

 annual mean for the daily variation of declination in the 

 magnetic needle, and the periodical frequency of the solar 

 spots, was first made known by General Sabine in the Phil. 

 Transact, for 1852; and four or five months later, without 

 any knowledge of the previous observations, the same re- 

 sult was enunciated by Rudolf Wolf, the learned Director 

 of the Observatory at Berne.* Lamont's manual of terres- 

 trial magnetism, 1848, contains a notice of the newest meth- 

 ods of observation, as well as of the development of these 

 methods. 



1840-1845. Bache, Director of the Coast Survey of the 

 United States, Observ. made at the Magn. and Meteorol. Ob- 

 servatory at Girard College, Philadelphia (published in 1847). 



1840-1842. Lieutenant Gilliss, U. S., Magnetical and Me- 

 teorological Observations made at Washington, published 1847, 

 p. 2-319; Magnetic Storms, p. 336. 



1841-1843. Sir Robert Schomburgk's observations of 

 declination in the woody district of Guiana, between the 

 mountain Roraima and the village Pirara, between the par- 

 allels of 4° 57' and 3° 39' (Phil. Transact, for 1849, pt. ii., 

 p. 217). 



1841—1845. Magnet, and Meteorol. Observations made at 

 Madras. 



magnetical operation of the central body of our planetary system, not 

 by its heat-producing quality, but by its own magnetic power, as well 

 as by changes in the Photosphere (the size and frequency of funnel- 

 shaped openings), gives a higher cosmical interest to the study of the 

 earth's magnetism, and to the numerous magnetic observatories (Cos- 

 mos, vol. i., p. 190 ; vol. v., p. 72) now planted over Russia and North- 

 ern Asia, since the resolutions of 1829, and over the colonies of Great 

 Britain since 1840-1850. (Sabine, in the Proceedings of the Roy. Soc, 

 vol. viii., No. 25, p. 400; and in the Phil. Trans. Jor 1856, p. 362.) 



* The treatise of Rudolf Wolf, referred to in the text, contains 

 special daily observation of the sun's spots (from January 1 to June 

 30, 1852) and a table of Lamont's periodical variations of declina- 

 tion, with Schwabe's results on the frequency of solar spots (1835- 

 1850). These results were laid before the meeting of the Physical 

 Society of Berne on the 31st of July, 1852, while the more compre- 

 hensive treatise of Sabine (Phil. Transact., 1852, p. 116-121) had 

 been presented to the Royal Society of London in the beginning of 

 March, and read in the beginning of May, 1852. From the most re- 

 cent investigations of the observations of solar spots, Wolf finds that 

 between the years 1600 and 1852 the mean period was 11*11 years. 



