590 
DE. VIKTOE VON LANG ON THE 
have the means of adjusting the delivering tube to a vertical position in order to avoid a 
displacement of the axis of the jet when the quantity of the water augments or dimi- 
nishes. Both purposes may be attained in the following way : — 
A wooden beam (B) is horizontally attached to the two walls forming the sides of the 
recess of a window. On it is fixed a brass plate (C) by means of two pulling and two 
pushing screws. The plate supports a vertical tube (D) of brass, 4 centims. long, and 
with an outer radius of IT centim. ; and this tube holds the delivering tube, which is 
cemented into it air-tight, and of course stands out at both ends. 
By means of the above-mentioned four screws the delivering tube can be rendered 
vertical, remaining at the time totally independent of the vibrations of the floor. 
The caoutchouc tube E that unites the delivering tube with the water-tap F below it 
is about one metre long and 0-3 centim. thick. The distance of the two ends of the 
caoutchouc tube is in vertical direction 30 centims., in horizontal direction 40 centims. ; 
strings fastened to the ceiling hold up the tube. 
By these arrangements it was possible to have continuous veins (W) of water of 
different lengths. The maximum lengths, however, could not be determined, the jet 
meeting, 130 centims. below the orifice, a board that was also fixed to the walls. If the 
quantity of water was so regulated by the tap F that the jet remained continuous till it 
reached the surface of the water in a vessel put under it, nothing was to be heard of the 
movement of the water, and the vein looked like a glass rod. 
This regularity was of course disturbed in the most unpleasant way as often as the 
water-pipes were made use of in neighbouring places. A pressure-gauge inserted into 
the conduit indicated, however, when the normal state was restored. This normal pres- 
sure of the water at the place of observation is four atmospheres. 
I have to describe now the special contrivances for the demonstration of the friction 
between the air and the continuous vein of water. There is first of all a crosspiece (G) 
made of glass tubes with an outer radius of IT centim. One of the four arms of this 
crosspiece has a length of 36 centims., the other three a length of 7 centims. The long 
arm is to be united air-tight by a caoutchouc tube with the lower end of the brass tube 
D, both tubes having on this account the same outer radius. In this position of the 
crosspiece two arms of it stand horizontally. An open manometer is fastened to one of 
these arms by means of a caoutchouc connexion ; the other arm leads to the “ measuring 
tube ” I, with which it is connected air-tight by a short caoutchouc tube. This tube I 
serves to measure the motion of the air caused by its friction on the jet of water in the 
“ aspirating tube ” K, the section of which does not very much exceed the section of the 
water vein. The aspirating tube is held up by the fourth arm of the crosspiece, with 
which it is united air-tight by a caoutchouc mouthpiece (L), such as is used for nursing 
children. The upper end of this tube was always brought to the height of the horizontal 
axis of the crosspiece, 35 centims. below the delivering orifice; the lower end was 
generally widened like a funnel to avoid disturbances by adhering drops. For the 
purpose of adjusting the aspirating tube so as to make its axis coincide with the axis 
