Hoyal Institution, 75 



resulting from the shock of two opposing liquid veins. In this case, 

 though the forces are in opposite directions, motion is not annihi- 

 lated ; but the liquid, as first shown by Savart, spreads out so as to 

 form a thin transparent film, the plane of which is at right angles to 

 the direction of the jets. By varying the pressure on one side or 

 the other, or by making the jets of different diameters, the plane 

 film could be converted into a curved one, and sometimes actually 

 caused to close, so as to form a pellucid sack. A cistern, situated 

 at the top of the house and communicating by pipes with the lecture 

 table, placed a considerable pressure at the disposal of the lecturer, 

 and enabled him to exhibit in a striking manner the various phseno' 

 mena described by Savart in his researches on the motion of liquids. 

 A vein was caused to fall vertically upon a brass disc upwards of 

 3 inches in diameter : the liquid spread laterally on all sides and. 

 formed an umbrella- shaped pellicle of great size and beauty. With a 

 disc of an inch in diameter, a pellicle of at least equal magnitude was 

 formed. When a candle was placed underneath the curved sheet of 

 water a singular effect was produced. The film above the candle 

 was instantly dissipated ; and on moving the candle, its motion was 

 followed by a corresponding change of the aqueous surface. Ou 

 turning a suitable cock so as to lessen the pressure, the curvature of 

 the film became increased, until finally the molecular action of the 

 water caused it to form a curve returning upon itself, and exhibit- 

 ing the appearance of a large flask, When the film completely 

 embraced the vertical stem which supported the brass disc, a change 

 in the form of the liquid flask was observed, the latter became elon- 

 gated, and was sometimes divided into two portions, one of which 

 glided down the vertical stem and was broken at its base. When 

 the jet was projected vertically upwards, large sheets were also 

 obtained. The jet was also suffered to fall into small hollow cones 

 of various apertures, and the shape of the liquid sheet received 

 thereby some] beautiful modifications. The enclosed sides of the 

 hollow cone gave the liquid an ascending motion, which, combined 

 with the action of gravity, caused the film to bend and constitute a 

 vase-shaped surface of great beauty. The lecturer next referred to 

 the constitution of a liquid vein ; he had pointed out, some years 

 ago, a simple mode of observing this constitution by means of the 

 electric spark ; this method corroborated the result before arrived at 

 by Savart, that the lower portion of a liquid vein owes its turbidity 

 to the fact of the mass being there reduced to drops, although the 

 quickness with which they succeed each other gives the eye the im- 

 pression of continuty. Savart's last experiments on this subject were 

 repeated : a tube about 5 feet long and 2 inches wide had a perforated 

 brass disc fixed at its lower extremity ; the tube was filled with 

 water, which, after it had become motionless, was permitted to issue 

 from an orifice pierced in the centre of the disc. As the liquid 

 escaped it gave birth to a succession of musical notes of sufficient 

 intensity to be distinctly heard throughout the theatre. That these 

 notes were not due to the motion imparted to the air by the descend- 

 ing drops of the liquid vein was proved, first, by intercepting the 

 vein in its continuous portion, and secondly, by permitting it tp 



