380 Miscellanies. 



tioning, that when a jet of water is discharged under mercury the 

 results are the same, under a given force, as when it takes place in 

 water or air, the quantity discharged being in all cases the same in 

 ihe same time. Hence, it appears that the force with which a mov- 

 ing or spouting fluid recoils, is not affected by the surrounding medi- 

 um, however rare or dense it may be ; and thus we may understand 

 why the attempts, which have been made to propel vessels, by forcing 

 water through them against water, have not proved advantageous. 

 The well known fact that large rivers penetrate in a direct course, far 

 into the ocean, notwithstanding, its agitation by tides and currents, is 

 somewhat analogous ; and were it not for this remarkable degree of 

 mobility in water, the sediment which is now mostly deposited at a 

 considerable distance in the sea, would accumulate near the mouths 

 of rivers and divert them from their courses. Whilst making my ex- 

 periments on the jet of water, I noticed that where sand was dropped 

 into the water near the orifice from which the jet issued, it was drawn 

 laterally toward the hole, till it distinctly appeared to enter it, but it 

 was in fact only an optical deception, the grains of sand being carried 

 away by the jet, as soon as they come into contact with it, with such 

 great velocity as to be perfectly invisible. — -Idem. 



4. On the discharge of a jet ofivater in water. — It has been proved 

 by Rob. W. and Alfred Fox, Esqs., of Falmouth, that a jet of water 

 discharges the same quantity in water as in air, in a given time, with- 

 out reference to the depth or motion of the water, at least within cer- 

 tain limits. When the head of water was six feet, the quantities dis- 

 charged were equal in air, in still watet, and in a rapid stream, and 

 when the jet was turned with the current or against it ; and when by 

 lengthening the tube, the aperture was submerged to the depth of 

 fifteen feet, the effect was the same as at the surface, under the press- 

 ure of an equal column above it. — -Phil. Mag. and Annals. 



5. dementis experiment. — An easy mode of performing this ex- 

 periment is this. — Holding the open hand horizontally, with the palm 

 downwards and the fingers close together, apply the lips to the inter- 

 val between the second and third finger, nearest the roots, and then 

 blowing with force, a strong jet of air will, of course, issue fi'om.the 

 aperture at the under side of the hand. Now put a piece of paper 

 or card three or four inches square against that aperture, and again 

 blow 5 the paper will not be blown away, nor fall by hs own weight, 



