TRANSACTIONS OF SECTION G. 1193 
2. The Forth Bridge Works. By Anpruw S. Biceart, C.L. 
See Reports, p. 873. 
FRIDAY, SEPTEMBER il. 
‘The following Papers were read :— 
1. The American System of Oil Pipe Lines. By J. H. Harris. 
2. The Movement of Land in Aberdeen Bay. By W. Smiru. 
3. On Shallow-draught Screw-steamers for the Nile Expedition. 
By J. T. THornycrort, M.Inst.C.H. 
A special feature of these steamers for use in shallow waters is the form of the 
‘hull in the neighbourhood of the propellers, it being such as to maintain a volume 
-of water, like a wave, over the propellers, even though they should extend above 
the water-line of the vessel. The author demonstrated the serviceableness of such 
-a form as early as 1875. 
The second special feature is the kind of propeller used. It resembles a screw, 
but is placed in a tube having guides to direct the stream aft, and a conical body 
to contract the area of stream. 
The principal dimensions of the Nile boats are given below: 
fiz air 
Length of hull at water-line ‘ i > . 140 0 
Beam moulded : . j , 21 0 
Load draught . é < , : * : 23 
Displacement . . 3 i d é .  98°6 tons 
With a light draught of 2 feet aft, 673 tons displacement, a speed of 15-1 knots 
~was obtained, while at the load draught trial, 2 feet 3 inches, the displacement 
being 93°6 tons, a speed of 14:17 knots was obtainable with an I H.-P. of 390. 
The displacement coefficient was 150. 
The vessel is arranged to carry guns on its upper deck, which is supported on 
Aullet-proof houses. On the fore part of the upper deck is a bullet-proof conning 
tower containing a steam steering engine. 
The hull is of steel divided into water-tight compartments ; the engines are of 
“the same model as used in the torpedo-boats by the author’s firm, and the boats 
are fitted with triple rudders in order to increase the steering power for the 
“Special purposes for which they are intended. 
-4, The Sphere and Roller Friction Gear. By Professor H. S. Here Suaw. 
The author described before Section A last year the principles involved in the 
-action of the ‘sphere and roller’ mechanism, a complete investigation of which is 
being published in the Philosophical Transactions of the Royal Society. Since 
that time the above principles have been further applied, the results of which may 
be seen in the mathematical instrument section and in the transmission of power 
-section of the Inventions Exhibition. The object of the author in the present 
paper is to speak only of the latter application, giving the results of actual trial 
-and a description of a new arrangement which is being made on a still larger scale. 
The author, first by means of diagrams, briefly explained the principles of the 
mechanism, in which a change of the imaginary axis of revolution of the sphere is 
