194 Miscellaneous Intelligence. 



of smooth cork may be used, and for the tin tube, a glass tube, or 

 one made by rolling up a piece of paper. 



If the tube be held horizontally, or inclining a little upward, 

 and a disk of card o.r paper be placed loosely against the aperture 

 in the plate, it will be found that, on applying the mouth to the 

 end of the tube, and blowing air through, that the disk will not be 

 driven away, but actually made to apply closely to the surface of 

 the plate ; and if turned towards the ground it will be found to re- 

 main opposite the hole, and not to fall until the current of air is 

 stopped. Even a plate of tin may in this way be suspended by a 

 current of air ; which at first would be supposed to conjoin with 

 gravity in forcing it to the ground. When the disk is flexible and 

 slightly elastic, a heavy sound, and sometimes even a shrill tone, 

 is produced by the vibrations of the plate. 



In explanation of this experiment, M. Hachette says, " The air 

 is pushed from the mouth A of the tube, towards the orifice E of 

 the plate ; it strikes the part of the disk opposed to this orifice, and 

 the mean pressure on that part is greater than the pressure of the 

 atmosphere. The blown air then takes place of that between the 

 plate and the disk opposed to it; it moves in this interval with a 

 velocity decreasing from the edges of the aperture : the elastic force 

 of this air decreases at the same time, so that its mean pressure 

 between the plate and the inner face of the disk becomes less than 

 the atmospheric pressure ; and as this last pressure is exerted on 

 the whole external face of the disk H, I, this disk, subject at the 

 same time to the two contrary pressures on its opposing faces, 

 obeys the greater, and is pushed towards the plate C D. 



It is not necessary that the disk, C D, should be near the orifice 

 E, of the tube A E. Let Fig. 2 be an instrument composed of 

 a hollow cylinder, C D F G, and a flat border of the dimensions 

 C" F, or G D". Let a tube, A E, be fixed to the bottom of the 

 cylinder, the orifice E having a diameter of about three millimeters 

 (0.12 of inch). If air be blown in at A, against the disk, H I, 

 in the neighbourhood of the flat border, the disk will be urged to- 

 wards the orifice E. This instrument is also delineated on a scale 

 of one half. The disk, with the attached weight, weighs about 

 12 grammes (184.87 grains), being 54 millimeters in diameter; 

 the pressure of the atmosphere upon it equals 23 kilogrammes : 

 from which it follows that, in this experiment, the pressure of the 

 air blown upon the inner surface of the disk, and the atmospheric 

 pressure exerted on the exterior of the same disk, only differs from 

 each other by about one two-thousandth part of the latter. — 

 AjiJf^ales de Chimiey xxxv. 34. 



^. Considerations relative to Capillary Action^ hy M. Poisson. — 

 M. Dutrochet, whilst explaining his views relative to the cause of 

 vital movement in plants and animals, stated that if an animal or 

 vegetable membrane were formed into a bag, having a tube of 



