742 
PROCEEDINGS OF SECTION H. 
No. of experiment. 
Velocity in miles per hour. 
Pressure in lb. per sq. ft. 
5 
6 
7 
8 
9 
10 
11 
12 
18 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
14*6 
15 
15*9 
17*2 
17*2 
17*6 
18*2 
19*3 
19*8 
20*4 
21*4 
22*3 
227 
24*4 
24*6 
24*6 
25*7 
25*7 
26*8 
•65 
•77 
•79 
•68 
*97 
113 
1*07 
1*13 
1-41 
1-36 
1*57 
1*90 
174 
1-97 
1*78 
2*02 
2*06 
2*15 
2*24 
These results, though presenting occasional anomalies due to the 
defects of the apparatus and imperfect observation, correspond very 
fairly with the formula, 
P= 0033 V 2 , 
which differs very little from Dines’ formula, 
P= , 0035 V% 
referred to in the previous paper, and. are utterly irreconcilable with 
either Crosby’s or Smeaton’s, as is shown by Fig. 1, where the 
experiments are shown by dots and the various formula? by lines. 
It should here be mentioned that the observed pressures were all 
increased by 10 per cent, to allow for niit-wind , or the general motion 
of the air in the room due to the action of the apparatus and friction 
of the mechanism. In doing this the example of Crosby was followed, 
whose reasons are fully given in Engineering of 13th June, 1890, p. 716. 
If this allow r ance be not made the formula will become, 
P=*003 V 2 . 
I regret that the position and construction of the gas engine prevented 
my extending the experiments to higher velocities. 
The next point left in a not thoroughly satisfactory state by my 
previous experiments was the effect of variation of angle of incidence 
on the normal pressure. The old apparatus, which consisted of a plane 
surface mounted on a carriage, had a tendency to overturn when the 
incidence was very oblique, and gave uncertain results. The uew 
apparatus consists of a plane surface attached to a balanced lever 
having a firm but nearly frictionless axis. This axis can be placed at 
an}' required angle. The motion of t lie plane is prevented by a thin 
cord leading to a spiral spring, and passing on its way round a small 
freely moving pulley on the axis of a small liy wheel. This latter 
arrangement was found very useful to check oscillations due to 
momentary gusts in the current of air from the blowing machine 
described on p. 577 of Yol. V. of the Trans. Aust. Assoc. 
