The thrust obtainable from a propeller depends on three variable quantities :

1. (1) The revolutions per second (n).

2. (2) The dimensions of the propeller.

3. (3) The slip (s).

Two further quantities are involved, the Torque (M) and the Power (H), but these are both dependent on the three preceding.

Assuming, in the first place, a constant slip (say, 100 per cent.), and choosing any convenient vaiue for the revolutions, we immediately fix a relation between the power consumed and the torque.

This exhibition, organised by the Society of Motor Manufacturers and Traders, Ltd., was held at Olympia from the 19th to the 27th March, 1909.

The aëronautical portion attracted considerable attention, and the Society is to be congratulated on the result of its efforts to interest the public in aëronautical matters.

It is not proposed in these notes to give an account of all the exhibits, but an attempt will be made to describe those in which the members of the Aëronautical Society of Great Britain are more especially interested. Motors are only briefly touched on, as they are discussed in Mr. McKinney's paper.