130 M. Fuss's Account of the Magnetical and 



a constant force, foi* measuring the intensity of the earth's 

 magnetism. I not only plunge them several times in boiling 

 water, but I cool them as often down to —20° or —25° of 

 Reaumur, which is not difficult in our climate. This method 

 has succeeded so perfectly, that I can recommend it to scien- 

 tific travellers. 



I have also established the existence of a daily variation in 

 the inclination of the needle and in the magnetic intensity, by 

 direct methods ; that is to say, by observing every day the 

 march and duration of the oscillations of a dipping-needle, very 

 long, and suspended on a knife-edge. I have found that the 

 inclination is several minutes greater at 11 d clock in the morn- 

 ing than at \\ o'clock in the evening. The intensity, on the 

 contrary, is greater iii the evening than in the moiimig. 



XXIX. Account of the Magnetical and Meteorological Obser- 

 vatio7is made at Pekin, by M. George Fuss. Communi- 

 cated in a Letter from M. A. Kupffer, of the Imperial 

 Academy of St. Petersburg, to Sir David Brewster, K.H. 

 LL.D. cSc. 



IV/r FUSS, the perpetual Secretary of the Academy of St. 

 -'-'-*• o Petersburg, has just communicated tome a letter 

 which has been addressed to him from Pekin by his brother, 

 who is at present with the Mission which the Russian 

 Government sends out every ten years. At my request the 

 Academy of St. Petersburg furnished M. Fuss (who set out 

 from this place in the spring of 1830,) with all the instru- 

 ments necessary for making magnetical observations. He has 

 with him two declination needles, one of which was executed 

 by M. Gambey of Paris, and which will serve also for ob- 

 serving the hourly variations of declination ; and these needles 

 will remain at Pekin after M. Fuss's return to Russia, about 

 the end of the present year. M. Fuss has also a dipping-needle, 

 which is also from the workshop of M. Gambey; — several 

 magnetic cylinders for observing the intensity, and a chrono- 

 meter, besides the instruments for astronomical observations. 

 The magnetical observations will be continued at Pekin, after 

 M. Fuss's departure, by M. Kowanko, officer of mines, who 

 will continue there during ten consecutive years. I send you 

 an extract from this letter, and beg that you will communicate 

 it to the Royal Society of Edinburgh*, and insert it in your 

 Journal. 



* The sittings of the Royal Society of Edinburgh were concluded before 

 the arrival of this letter. 



