Electro-Magnetism — Chemistry, 1 83 



the cold being at — 40° of Reaumur ; so that the frozen quicksilver could 

 be cut with a knife. On the 31st they arrived at Tomsk ; on the 21st of 

 January 1829, at Krasnojarsk ; and on the 7th of February at Irkutzk, 

 which is about 4000 versts from Tobolsk. They afterwards visited 

 Kiachta, and crossed the frontier of China ; but the most agreeable result 

 is, that one of the desired objects of the journey is accomplished, as the 

 observations have proved perfectly satisfactory — and the position of the 

 magnetic pole is ascertained. Centuries may elapse before Siberia will be 

 again so thoroughly observed. When the letters were dispatched, it was 

 resolved that the journey should be extended to Neertschinsk, from which 

 place Professor Hansteen would return to Krasnojarsk. His companion. 

 Lieutenant Due, was to go alone to Jakutzk, 2,700 versts N. E. of Irkutzk, 

 and perhaps proceed down the river Lena to the Frozen Ocean, and they 

 intend to meet again at Jeniseisk in September or October. 



ELECTRO-MAGNETISM. 



8. Laiu of the phenomena attributed to magnetism in motion. By M» 

 Saigey. — From a series of valuable experiments made with discs of cop- 

 per, zinc, tin and lead, M. Saigey has found that their action on a magne- 

 tic needle may be thus expressed. Calling x the distance of the needle 

 from the disc, and y the number of oscillations which it loses by the action 

 of the disc, or the difference between the number of its oscillations while 

 oscillating alone, and while oscillating under the influence of the disc, and 

 a and b two constant quantities 



y=ab ' 



that is, the oscillations lost form a progression by quotients when the dis- 

 tances of the needle from the discs form a progression by differences. 



Two numbers expressing the losses are necessary far calculating all the 

 others, for we must determine the two constants a and b in the formula 

 which expresses them, the first of these a indicating for example the loss 

 at the unit of distance, and the second b the quotient of one loss divided 

 by the following. 



The constant a varies for different amplitudes in the oscillations; but 

 the ratio b is invariable for all amplitudes. 



The constants a and b increase in an inverse order not only for different 

 metals acting on the same needle, but even for the same metal acting up- 

 on different needles. — Annales d' Observation y No. i. p. 48. 



II. CHEMISTRY. 



9. Professor Erman on the Phenomena of Liquefaction in different Bodies 



\ 2 Bismuth. 



Water. Alloy of Vl Lead. Phosphorus. 

 j 1 Tin. 



1. It dilates by congela- 1- It is condensed by so- 1. It is condensed by 

 tion. lidification. solidification. 



2. Its dilatability is 2. Its dilatability is sen- 2. Its dilatability is Zew 

 greater after congelation sibly equal before and af- after solidification than be- 

 than before it. ter solidification. fore it 



