196 REPORT—1840. 
wanted or could be introduced, that the timber viaducts were the most 
ceconomical. In ordinary heights of 50 or 60 feet, and with arches of 
less span than 100 feet, and particularly in countries presenting facili- 
ties for construction of stone, these latter would be undoubtedly prefer- 
able ; but when the height of the construction became great, the great 
expense for the centering for arches of masonry, and the multiplication 
of the number of piers, in order to keep the span of the arches to a 
moderate size, greatly increased the expense, and threw the balance 
vastly in favour of the timber. Mr. Vignoles instanced the Ribble 
Viaduct on the North Union Railway, which was about 50 feet high, 
with five large arches, of 120 feet span, and had cost 60/. per lineal 
foot ; whereas, in another place, a timber viaduct, of 140 feet high in 
the centre, and averaging 100 feet high, with arches of 130 feet span, 
and extending for a length of nearly 2000 feet, was proposed, which 
would not exceed in price 20/. per lineal foot, the breadth of roadway 
being, in both cases, 28 feet for a double line of rails. Mr. Vignoles 
stated, that in extending lines of railway through the west of England 
to the packet stations, through the mountains of Wales for a commu- 
nication between London and Dublin, and through many parts of 
Treland, along the lines laid out by him for the Government Railway 
Commissioners, the timber viaducts would, from their cheapness, 
enable the works to be entered upon, which the great cost of stone 
would quite forbid. 
On the Safety Rotation Railway. By Mr. Hawkins. 
Mr. Hawkins exhibited a model of a railway and carriage, recently 
patented by Mr. Rangeley under the above title. It is an inversion 
of the ordinary construction, inasmuch as wheels are made to revolve 
on fixed bearings, placed in two parallel lines along the road; and 
the carriage, without wheels, is built upon a pair of running rails, 
carried along upon the peripheries of the train of wheels kept in 
revolution by steam-engines fixed at every mile or two of the road. 
It is intended to have the wheels three feet diameter, and three feet 
apart, which will give 1760 wheels on a mile. They are to be driven 
by a succession of endless bands, one band in every case passing 
around two pullies attached to every two contiguous wheels. The 
carriages are designed to hold forty passengers each, with their lug- 
gage ; the whole, including the carriage, not to exceed five tons ; the 
running rails always to bear on eight or ten wheels, so that no wheel 
shall have to support more than about ten or twelve hundred weight. 
The wheels, therefore, need not weigh more than half a hundred 
weight each, to be sufficiently strong for supporting the carriage. It 
is found by experiment, that three ounces suspended from the peri- 
phery of such a wheel causes it to revolve. Any weight that sets a 
wheel in motion, will, if continued, cause the same to revolve with ac- 
celerated velocity, until the resistance of the atmosphere becomes equal 
to the accumulated force, after which a steady speed will be kept up. 
It is inferred from observation, that the wheels driven with a continued 
