ftdO M. A. Seccbi on the Periodical Variations 



contribution the work done in other magnetic observatories, and 

 especially in that established at Makerstoun in Scotland, at his 

 own expense, by Sir Th. Makdougall Brisbane, and reduced by 

 Mr. Allan Broun, a work valuable for having been performed for 

 the express purpose of examining whether the heavenly bodies, 

 and especially, the moon, influenced the needle. 



The Russian works and publications are also very important, 

 because made in observatories formed on the same system as thfe 

 English, and now published regularly from 1841, under the care 

 of M. Kupffer, Director of the Central Physical Observatory of 

 Russia. They form a collection of many volumes, and a special 

 one, published in 1852, contains the results of the Magnetical 

 and Meteorological Observatories of Petersburg, Catherinenburg, 

 Barnaoul, Nertchinsk and Sitka, besides an immense number 

 of data registered in upwards of twenty volumes, published 

 under the title of Annuaire Magnetique et Meteorologique du 

 Corps des Ingenieurs des Mines, St. Petersbourg, which give all 

 the observations made in the Russian empire and at Pekin. 



Adding to this the many magnetic observatories established 

 at various points in Italy, and (more especially) in Germany, in 

 Holland, Sweden, the United States of America, and elsewhere ; 

 the many observations made and collected by the indefatigable 

 and learned Quetelet, inserted in the Transactions of the Aca- 

 demy and Observatory of Brussels ; and lastly, the long series 

 made by Arago at Paris, — and it will perhaps be seen that there 

 is no branch of physical science in which more laborious and 

 copious researches have been made than in this.* 



A good part of the magnetic observatories which have been 

 cited, and especially those of the British Colonies, are now out of 

 activity ; but the fruits collected remain, and it will be difficult 

 in future to do more, or at least more useful work, than that 

 which has been done. Rather a wise and intelligent oeconomy 

 requires that there should first be derived as much as possible 

 from what has been obtained, in order to find out what direc- 

 tion should be given to new researches, when the materials 

 afforded by the old shall be exhausted. Until such a period shall 

 arrive, it is sufficient for the progress of science to have here and 

 there a few centres of observation, and at this moment several 

 such subsist. The most imposing of these is that of Greenwich. 

 Its system of observation by photographic registration is the 



immense assistance in the analysis of the phaenomena. If all the ma^etie 

 publications had been furnished with reductions of this kind, we should 

 have been able greatly to enrich the present memoir, but unfortunately 

 they are rendered useless to us by the total or partial want of such a pre- 

 limmary digest, which we have not ourselves the time or the means of 

 supplying. 



