656 REPORT—1883. 
(1.) The speed of the fan at even moderate velocities is not proportional to the: 
speed of the water. 
(2.) It is impossible to maintain the same conditions of friction for more than a 
yery short time of working, especially in impure water. 
(3.) They stop altogether at low velocities, 
The first involves considerable expenditure of labour if the records of observa- 
tions at low velocities are to be worth anything at all. In the first place the meter 
must be carefully rated at a number of different velocities, and this without 
elaborate appliances is a difficult matter to accomplish. The result of such a 
rating made by Mr. R. E. Froude, at the Admiralty Experimenting Works, 
Torquay, is shown by the curve (exhibited on a diagram), by which the second 
and third objections were made evident as well as the labour involved by the first.’ 
It was with a view of overcoming the foregoing objections that the instrument 
exhibited was contrived by the author. A description of this was then given,. 
and its advantages were explained, as well as some of the results obtained by it. 
2. A Flexible Band Dynamometer.} 
By Professor W. C. Unwin, M.Inst.C.H. 
The ordinary flexible band dynamometer consists of a band passing over a brake 
pulley with a fixed weight at one end and a spring balance on the other. The: 
difference of the tensions measures the friction, and the product of this and the 
velocity of the pulley gives the work absorbed. The chief difficulty in using it is 
that the oscillations of the spring balance make the determination of one of the 
tensions inexact. By taking the band over an idle pulley and back over the brake- 
pulley, the tension to be measured by the spring balance is made very much less, 
and the effect of errors in measuring it has less effect on the determination of the 
work absorbed. 
3. Curves of Air Resistance. By Professor GREENHILL, M.A. 
The author presented a series of curves plotted from experiments by Mr. 
Bashforth and Herr Krupp, of Essen, on the velocities of projectiles. In these 
curves the abscissee represented velocities and the ordinates resistances. At low 
velocities the curve was a parabola, but at the velocity of sound it suddenly 
stepped up and pursued another parabola at a constant height above the first. At 
the speed corresponding to efflux into a vacuum the curve rejoined the original 
parabola, and followed the law that the resistance varies as the square of the 
velocity. The part of the curve between the two limits also followed the same 
law with a constant added. In Mr. Bashforth’s experiments the velocity varied 
from 100 to 2,800 feet per second, and the resistance was tabulated in pounds per 
circular inch. In Krupp’s experiments the speeds varied from 140 to 700 metres 
per second, and the results were given in kilos. per square centimetre. His curve 
lay below Bashforth’s, indicating a lower resistance, due to difference in the shape 
of the head of the projectile. The lowest velocity of 100 feet per second, or 70 
miles per hour, overlapped, the author said, those dealt with im meteorology and 
engineering, and gave only a pressure of 10 Ibs. per square foot. At 2,800 feet per 
second the pressure was 35} Ibs. per circular inch, or 6,500 Ibs. per square foot. 
These results did not agree with those deduced from wind pressures. 
4, Southport Sewage.* By Isaac SHONE. 
By the aid of maps, sections, and diagrams, the author explained his semi- 
pneumatic and semi-hydraulic system of collecting and ejecting sewage-proper within 
flat town areas, such as obtain in Southport. His system, while it was specially re- 
commended by him for draining low-lying and flat towns on the ‘separate system,’ 
1 The Hngineer, October 1883. 
2 Published in extenso by the author (Wrexham). 
