594 
DE. VIKTOE YON LANG ON THE 
The constants of these formulse have been determined by the method of least squares 
from the corresponding values of r found by direct observation. The last formulse give 
for W=20 and W=30 the following numbers for r : — 
w . 
z. 
r\ 
r—r'. 
20 
35 
2-090 
2-085 
+ 0-005 
45 
1-989 
1*957 
+ 0-032 
55 
1-884 
1-865 
+ 0-019 
65 
1*791 
1*795 
— 0-004 
75 
1*689 
1-741 
-0-052 
30 
35 
2*542 
2-567 
-0-025 
45 
2-408 
2-404 
+ 0-004 
55 
2-297 
2-287 
+ 0-010 
65 
2-157 
2*198 
-0-041 
75 
2-181 
2-129 
+ 0-052 
The calculated values of r denoted by r' were found by the formulse 
W=20 0*9976 + 6*4342 
y/z 
30 1*1819+8*1973 -L 
v* 
the constants of which were also determined by the method of least squares from 
the foregoing values of r. The calculated numbers agree in this case too with the 
observed ones, as well as is necessary for the present purpose. From the last two 
formulse the following equation, 
r=0*6290+ 0*01843 W+(2*9080 + 0*17631 W) -U 
V % 
was finally deduced, which gives the radius of the jet for any height and quantity of 
water. Expressing the turns of the micrometer-screw by centimetres, we have, in 
accordance with the value given above for these turns, 
r=0*09246 +0*002709 W+ (0*42748+ 0*025918 W) i. 
Determination of the Volume of the Aspirated Air. 
I have already explained the method used for measuring the volume of the aspirated 
air. However, the question arises whether, in following this method, the volume 
measured by the motion of a soap-lamina is really equal to the volume that is aspirated 
when the measuring tube is quite open. First of all the weight of the lamina might be 
of influence, acting in a sense contrary to the movement of the air. But the experiment 
can easily be arranged in such a way that the weight of the lamina favours the air’s 
