184 Scientific Intelligence. — Natural Philosophy. 



mode of shaking upon the molecules in the direction of the sur- 

 face, which would seem to render it probable that these pheno- 

 mena arise from a vibratory motion transmitted by these mole- 

 cules. The second method which M. Becqiierel employed for 

 observing the electrical effects of friction in metals, was in- 

 vented by M. Singer ; but M. Becquerel eff*ected import- 

 ant modifications in it, without which he could not have 

 made the observations which he detailed in his memoir. This 

 process consists in taking a plate of metal, which is kept 

 inclined while metallic filings are thrown upon it, which are 

 received in a metal capsule, communicating with a very de- 

 licate electroscope. The filings, in their passage over the plate, 

 acquire an electricity, which is owing to the friction, and not to 

 an act of contact, as M. Becquerel proved in a direct manner. 

 The filings of a metal are negative with relation to a plate of 

 the same metal. Zinc filings are positive with gold, platina, 

 silver, iron, bismuth, and lead, while they are negative with 

 tin, antimony, and cadmium. In general, metallic filings^ when 

 they fall upon a plate of metal, have a tendency to assume the 

 negative electricity. This tendency, however, does not prevent 

 the filings of a positive metal from being positive with relation 

 to the more negative metals. 



2. On the Variation of the Freezing Point in Mercurial 

 and Spirt of' Wine Thermometers ; by M. Yelin. — M. Bellani 

 appears to be the first who discovered, in 1808, that the freezing 

 point is liable to vary. He mentioned it in the Pavia Journal 

 of Natural Philosophy ; but his observation did not attract the 

 attention of philosophers, and was forgotten, until the editors of 

 the Bibliotheque Universelle took the subject in hand. Of 

 twenty-one thermometers which M. Yelin submitted to a new 

 examination, there was only one that retained its original freez- 

 ing point. In most cases the freezing point was too high, so as 

 to correspond sometimes to -f- T. Cases, however, were met 

 with in which it was too low, — Kastners Archiv, t. ii. p. 109. 



METEOllOLOGY. 



3. On the Weight of' pur e Atmospheric Air. — Br Prout is at 

 present occupied with the investigation of this important sub- 

 ject ; and though he has not yet brought his researches to a 

 conclusion, he permits me to state, that 100 cubic inches of pure 



