British Association for the Advancement of Science, 319 
Staves; the figures being engraved on copper plate, on an en- 
larged scale. Mr. T. Motley gave an account of a suspension 
bridge over the Avon, Tiverton. The peculiar feature of this 
bridge is, that each chain is attached to the roadway, and the 
suspending bars are carried up through each chain above it. The 
length of the bridge is 230 feet, the breadth 141, and the cost, 
including the towers and land abutments, under 2,400 
Prof. Willis described his instrament ‘called the Cdeeieanhy 
designed for enabling workmen to find at once the centres from 
which the two portions of the tooth are to be.struck, so that the 
teeth may work truly together. 
Mr. Lang described some improvements in Ship Buélang, 
and exhibited models illustrating the Beary keel, which had been 
introduced with great success. 
Count Augustus Breunner communicated a paper on the use of 
wire ropes in deep mines. About seven years ago, ropes compo- 
sed of twisted iron-wire, ‘were introduced into the silver mines of 
_ the Hartz mountains, as a substitute for the flat ropes. previously 
in use. Since that time they have been adopted in most of the 
Mines of Hungary and Austria, to the almost total exclusion of 
flat and round ropes made of hemp. ‘These iron ropes are as 
strong as a hempen rope of four times the weight. One has been 
in use upwards of two years without any perceptible wear, 
whereas a flat rope performing similar work, would not have lasted 
more. than a single-year. ‘The diameter of the largest rope in 
common use in the deepest mines of Austria, is one inch and a 
half. This rope is composed of iron wires, each two lines in di- 
ameter ; five of these are braided together into strands, and three 
of these strands are twisted tightly into arope. . Great care is re- 
quisite in making the rope, that the ends of the wires be set deep 
in the interior of the rope, and that no two ends meet in the same 
part. The strength of these ropes islittle less than that-of a solid 
‘fron bar of the same diameter. The usual weight lifted is 1000 
‘pounds. ‘The rope on leaving the shaft, must be received ona 
cylinder of not less*than eight feet diameter, and be kept well 
coated with tar. ‘There is a saving of about oné third of the 
‘power in one case mentioned, for four horses with a wire rope, 
- are doing the same work as szz horses with a flat ro 
Mr. Babbage called attention to some specimens of a new 
Method of wood engraving, by-Mr. G. Woone. 
