194 Miscellaneous Intelligence, 



It is about 3 atmospheres wrong at the highest pressure. — Bib, 

 Univ. xlii. p. 338.— B?//Z. Univ. A. xii. 407. 



3. On the Motion of Currents in Liquids. — M. Dutrochet has 

 made some singular remarks on the influencing causes of the mo- 

 tion of currents in liquids, and has found light to affect them 

 considerably. He finds that difference of temperature is the effi- 

 cient cause, and that l-800th of a degree of difference is sufficient, 

 when aided by light. In the absence pf light such motion will 

 cease. When the windows of the experimental room are closed 

 so much as only to admit light enough to distinguish, whether 

 the circulating motion continues or not, it soon ceases ; when 

 re-opened, the motion recommences. When completely suspended 

 by the absence of light, if the table be struck with slight blows, 

 the vibration communicated immediately causes the motion to re- 

 commence ; when the liquid was again at rest, the sound of a vio- 

 loncello, or a bell, was occasioned, and the vibrations communi- 

 cated to the liquid, again caused it to acquire circulating motion. 

 Hence it would appear that the vibration of the particles of a 

 liquid favour the circulating motion which a slight difference of 

 temperature is competent to produce; that this previous vibration 

 is a necessary circumstance, and that light consequently only acts 

 by producing it amongst the particles of the fluid. From whence 

 M. Dutrochet concludes, that, in the phenomena of circulating 

 motion in liquids, two causes intervene — the efficient one, difference 

 of temperature, the favouring one, light, or any other circum- 

 stance which can communicate feeble vibrations to the particles 

 of fluid. — Uevue Ency., xlv. 234. 



4. On the Expansive Force of Freezing fVater. — Experiments on 

 the force exerted by water when it becomes solid, have been made 

 in the Arsenal at Warsaw, during the winters of 1828 and 1829. 

 Howitzer shells were ijsed for the purpose ; they were of cast iron, 

 6 inches 8 lines in diameter, the aperture 1 inch 2 lines in diame- 

 ter, and the thickness of metal I inch and 2 lines. One, 46.29 

 cubical inches in capacity, was filled with water at 41° F., left 

 open and exposed to the air at 21° F. : the frozen water formed a 

 projecting cylinder of ice of the diameter of the aperture, which 

 in two hours was 2 inches and 2 lines in length ; this was the maxi- 

 mum effect, and shewed that the water, by freezing, had under- 

 gone an expansion of 2.31 cubic inches, or -^ of the whole volume. 

 Another shell, after being filled with water, had the aperture 

 closed by a wooden plug ; it was then exposed to the same cold 

 as before, the plug was driven out, and the ice occupied its place. 

 Another shell, after being filled with water, was closed by an iron 

 screw, perforated by a hole 3 lines in diameter, the temperature of 

 the air was the same ; after seven hours the shell was burst into 

 two unequal parts, the larger being thrown a foot, and the smaller 

 10 feet from the place ; the ice had been formed to the thickness 



