SCIENTIFIC SUMMARY. 
435 
MECHANICAL SCIENCE. 
Road Tramways, — A new system of tramways for common roads^ intended 
to oUviate some of the objections to those previously introduced, is proposed 
by Messrs. G-. Eemiugton & Sons. 
Railway Tracklayer. — A paragraph quoted in Engineering from a Cali- 
fornian j ournal describes a machine introduced on the Pacific Railroad for 
laying the rails and sleepers during the construction of the line. The 
machine consists of a car 60 feet long with an engine for working the lifting 
machinery, which deposits regularly on the line the sleepers and rails in 
their proper position. The machine is pushed forwards by a locomotive, 
and the work is done so rapidly that 60 men are required to wait on it, but 
they do more work than twice as many could do on the old system. It is 
said to be able to lay five or six miles of track per day, or twelve times the 
usual rate by hand. 
The Glatton. — The Admiralty have just commenced to built at Chatham 
Dockyard a turret vessel surpassing in defensive power any hitherto con- 
structed. This vessel — the Glatton — is to be of 2,700 tons burden, 245 feet 
long, and 49 feet beam. Her exposed sides are to be covered with 12 inches 
thickness of iron, and her single turret with 14 inches, laid on teak backing 
10 inches thick, with the usual inner skin plating. She is to be armed with 
two 25-ton guns, and driven by engines of 600 horse power (nominal). 
Her speed will not be great, as she is intended for coast defence. Her 
draught will be 19 feet, and she is to be built from the designs of the Chief 
Constructor of the Navy. 
Propidsion of Ships . — Mr. C. W. Merrifield, E.R.S,, has called the atten- 
tion of the British Association to the slender basis on which theories of the 
motion of bodies in resisting media are founded, and particularly to the great 
deficiency of experimental knowledge on which to establish the laws of the 
propulsion of vessels. He proposes that experiments should be made, not 
on models, but on a large scale. He wishes to have ascertained, not only 
the exact motive power exerted in driving the vessel, but the velocity and 
direction of the currents of water at every po nt in the neighbourhood of the 
vessel in which it may appear useful to observe them. It is ob’sfious that 
no private person can carry out such experiments except at a ruinous cost in 
chartering vessels, whilst a Government maintaining a fieet in time of peace 
may not unfrequently be able to detail both suitable ships and scientific 
officers, for experimental objects, instead of simply cruising for exercise. 
He therefore suggests to the Association to memorialise the Government, 
stating their opinion as to the value of such experiments and as to the 
proper mode of carrying them out. Mr. Merrifield has himself made several 
suggestions as to the latter point. 
Resistance of Ships. — Professor Rankine has called attention to a neglected 
element in the resistance of ships, depending on the excess of the speed of 
the ship over the natural speed of the waves accompanying her, which 
natural speed depends on the depth to which she disturbs the water. Pro- 
fessor Rankine gives the results of three observations of the speed of advance 
of the obliquely diverging waves raised by ships. He has calculated the 
