^'f^ Scientific Intelligence. 



The mass of cloud now appeared to move more rapidly toward the north- 

 east, when the luminous flashes were almost incessant, and the light bril- 

 liant beyond description. The whole north-east horizon, during three 

 hours, being constantly lighted up either by widely diffused flashes or by 

 brilliant sparks and luminous coruscations, which were occasionally of a red 

 colour ; they appeared to strike in all directions, and one in particular was 

 observed to ramify in various directions like radii from a common centre. 

 There were during the evening several shooting stars, some of them of 

 great brilliancy. These phenomena continued until midnight, when the 

 clouds sank in the north east. The lightning was not followed by thunder 

 after the clouds had passed the town, and it was, when heard, rather indi- 

 stinct. The wind died away at 10 p. m. but sprang up again from the 

 east at about 11, with a moderate breeze. The barometer again rose after 

 midnight, and the next day it blew a gale of wind from the west, the 

 force varying from 5 to 8lbs. on a square foot. 



As the preceding very curious phenomena were observed by Mr Snow 

 Harris, an eminent and scientific meteorologist, our readers may depend 

 upon their perfect accuracy. 



ACOUSTICS. 



IS. Sounds of Gas issuing under great pressures, — It was observed by M. 

 Clement that a species of suction took place at the orifice of a tube when 

 a current of gas or steam escaped under considerable pressure. A metallic 

 plate was thus suspended, as it were, at the orifice. M. Clement had no- 

 ticed that the plate thus suspended emitted sounds extremely grave and 

 disagreeable. M. Savart, on the other hand, observed that they were 

 sometimes acute and very agreeable ; and having strewed sand upon the 

 surface of the plate, he discovered, from the manner in which it arranged it- 

 self, that the sounds are the results of a molecular vibration similar to that 

 which would be produced by the friction of a bow on the edges of the plate, 

 and not of a vibration of the air, analogous to that produced by the mouth- 

 pieces of wind instruments. One of the consequences of this explanation 

 is, that the sounds ought to vary with the size of the plate, which is actual- 

 ly found to be the case. 



14. M. Savart on a new fact in Acoustics,— On the 30th July, M. Sa- 

 vart announced a new fact in acoustics to the Academy of Sciences, name- 

 ly, that when the vibrating parts of a body are susceptible of displacing 

 themselves in the body, preserving their respective positions, ihei/ may 

 either oscillate round their first position, or enter into a continued motion 

 of revolution. The first case takes place when the vibratory motion has 

 been communicated by means of a single stroke of the bow ; the second 

 when several repeated strokes of the bow have been given at small inter- 

 vals. The experiment may be made in two ways with a circular metaUic 

 plate, either by means of sand placed on the plate, which, according to the 

 circumstances, takes one or other of the above movements, or by making 

 the rays of the sun fall upon the plate, and observing the image which 



