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 instrument called the Odontography 

 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 Building, 

 and exhibited models illustrating the safety keel, which had been 

 introduced with great success. 



Count Augustus Breunner communicated a paper on the use of 

 loire 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 a rope. 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 is little less than that of a solid 

 iron bar of the same diameter. The usual weight lifted is 1000 

 pounds. The rope on leaving the shaft, must be received on a 

 cylinder of not less than eight feet diameter, and be kept well 

 coated with tar. There is a saving of about one third of the 

 power in one case mentioned, for four horses with a wire rope, 

 are doing the same work as six horses with diflat rope. 



Mr. Babbage called attention to some specimens of a new 

 method of wood engraving, by Mr. G. Woone. 



