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XXIII. Experiments on the Friction between Water and Air. By Dr. Viktor yon Lang, 
Professor of Physics in the University of Vienna. Communicated by N. S. Mas- 
kelyne, M.A., F.B.S., Professor of Mineralogy in the University of Oxford. 
Received February 28, — Read April 6, 1876. 
We have only a few notices on the subject of the friction between air and water, and 
these few contradict each other. J. B. Venturi* states that the air put into motion 
by a jet of water moves light bodies. G. Magnus f opposes this, as he finds that a flame 
brought near to a vertical jet of water indicates no motion of the surrounding air. The 
following experiments show, however, that great friction does really take place between 
water and air, so great as scarcely to differ from total adhesion. 
But it is very much to be doubted whether Venturi was acquainted w T ith this pure 
friction between water and air, as he does n I say any thing about the constitution of his 
jets. It must be remembered that Venturi experimented long before Savart, who was 
the first to distinguish the two parts of a vertical jet of water, the continuous part and 
the other broken up into drops. The above-mentioned phenomenon can be demonstrated 
only on the first part, though the discontinuous part of the jet moves the surrounding 
air too, and with much more energy. But in this case Magnus was quite right when 
he attributed the motion of the air to other causes. 
Description of the Apparatus (Plate 52. figs. 1 & 2). 
After what I have just said it is clear that I had to begin my experiments with pro- 
ducing a continuous vein of water. Magnus gives the necessary directions ; but he lets 
the jet flow immediately from the reservoir, whilst I wished to use directly the conduit 
by which the city of Vienna has recently been supplied with water from the mountains. 
There is no doubt that in this way many inconveniences would be avoided, that make 
the method of Magnus and his predecessor Savart tolerably troublesome. After a good 
many failures I succeeded at last, principally by inserting a caoutchouc tube between 
the water-tap and the delivering tube A. 
The latter tube is of glass, 8 centims. long, outer radius 0'72 centim., inner radius 
0 - 54 centim. It is not plane at the lower end, but irregularly indented. 
The whole delivering apparatus must be set up in a very solid way ; even the slightest 
shake is sufficient to break up the continuous jet into single drops ; besides one must 
* Recherches experimentales sur le principe de communication laterale dans les fluides, applique a Impli- 
cation de differents phenomenes hydrauliques. Paris, 1797. 
t “ Uber die Bewegung der Fliissigkeiten,” Poggendorpf’s Annalen der Physik und Chemie, Band Ixxx. (1850). 
MDCCCLXXVI. 4 N 
