SECTIONAL TRANSACTIONS.—G. 435 
warrant recourse to more costly apparatus, the compressed air tunnel nearing com 
pletion at Teddington, and the large wind tunnel which will be erected at Farnborough. 
Between 1915 and 1919 three wind tunnels were erected at the Royal Aircraft Estab- 
lishment. These take the form of tubes of square cross-section, through which air 
is drawn by a fan at the outlet. The model is thus tested in a stream bounded by 
four walls. The smallest of these tunnels has recently been removed and replaced 
by a 5ft. open-jet tunnel closely modelled on that built by Prandtl at Géttingen. 
Tn this tunnel the model is tested in a free stream of air flowing across the test chamber. 
The tunnel requires only one-fifth of the power required by a corresponding tunnel 
of the other type. The absence of walls around the model facilitates experiment. 
The maximum wind speed is 115 m.p.h. It is intended to increase it to 250 m.p.h. 
by installing a larger motor. The diameter of the jet is 5 feet. 
A jet of circular section is suitable for many purposes, but an elliptic section would 
be best suited for tests of complete models. The major axis should be about 1-5 
times the minor axis. A jet of 10 ft. by 15. ft. section could be obtained in the building 
housing one of the present larger tunnels, which are 7 ft. square. 
The large tunnel which is to be erected at the Royal Aircraft Establishment will 
have an air circuit identical in form with that of this 5 ft. open-jet tunnel. The wind 
stream will have a diameter of 24 ft., and attain a speed of 120 m.p.h. Owing to the 
accessibility of the air stream it can be arranged that two of the actual aircraft which 
will be tested in this tunnel can be prepared for test at the same time in an adjoining 
hall and moved quickly by cranes into the stream. The tunnel will also be used for 
tests of large-scale models, and similar arrangements are being incorporated overhead 
for the preparation of the models and their rapid movement to and from the stream. 
A special ventilating system will remove poisonous exhaust gases when the engine 
of an aircraft under test is running in the stream, and this will also serve to keep down 
the rise of temperature during tests. 
When a full-size aircraft is under test in this tunnel the wings will extend beyond 
the stream. It will not be possible to obtain the lift and resistance of the whole 
aircraft, but the effect of variations in the central parts will be obtainable on the 
actual aircraft, and this information should prove of great value. 
There is also in course of construction a wind tunnel in which the air flows vertically 
upwards, and the model will not be fixed to balances but will be in free flight. This 
tunnel is for investigating the motion known as a spin, from which the pilot is some- 
times unable to effect recovery to normal flight. The model will be mounted on a 
vertical-axis bearing upon which the wind will cause it to rotate and ultimately to 
rise into a free spin. The upcurrent annuls the descent of the spinning aircraft 
and a spin of indefinite duration can be observed at close-hand. 
AFTERNOON. 
PRESIDENTIAL ADDRESS AND BRAMWELL Trust LEctTURE by Sir ALFRED 
Ewine, K.C.B., F.R.S., on Power (see page 122.) 
Monday, September 28. 
Brigadier-General C. H. Mircuent, C.B., C.M.G.—Engineers’ Contributions 
to Canada’s Development. 
Canada is but a new country and its engineering progress is measured only by 
decades. It cannot be said that its engineering dates back for a hundred years; 
rather is it more nearly fifty or seventy-five. 
Canada’s first people, coming originally from France three hundred years ago 
and from Britain a hundred and fifty years later, occupied only the regions around the 
Atlantic coasts and the Great Lakes. It was but seventy-five years ago that the 
- expansion began, and it is not much more than fifty or sixty years since the definite 
movement of population commenced to the prairie regions westward of the Lakes 
and to the Pacific coast. 
The population to-day, now about ten millions, is confined mainly to the Atlantic 
Provinces, to the regions about the St. Lawrence and the Great Lakes, and to a belt 
not more than three or four hundred miles wide stretching across the western prairie 
FF 2 
