MECHANICS AND USEFUL ARTS. 55 



of this kind, in which two or three spirals revolved in opposite ways to 

 prevent acceleration. The author then described a meter invented by Mr. 

 Chadwick, of Salford, which had recently been brought under his notice, 

 and which it was stated only varied five per cent, between a head of water 

 of one foot and one of 300 feet. In this meter a wire gauge or sieve was 

 introduced between the supply pipe and two inlet passages situated in the 

 bottom of a cylindrical vessel. These passages opened into two vulcanized 

 India rubber bags, which were bedded and laid fiat on the bottom of the 

 vessel, and there were openings at the other extremities of the bags for 

 allowing of the exit of the water into the meter. Ou the water entering 

 these bags it set in motion three conical rollers attached to a central spindle 

 in connection with the ordinary counting wheels and dial, each revolution 

 of the rollers, registering exactly the contents of the bags. About two 

 years ago the Corporation of Manchester advertised for a water-meter capable 

 of measuring correctly under variable and great pressure. This was 

 responded to by a large number of persons, and among others by Mr. Taylor, 

 who had had his attention for some time previously directed to the subject. 

 His meter consists of a cylindrical vessel or cistern, of a size proportioned 

 to the bore of the pipe that was to receive and discharge the water. Inside 

 the above-mentioned vessel there was a drum revolving on its axis in a 

 vertical or upright position, and the stream passing through the meter was 

 distributed upon the drum at each side of the meter. The registration was 

 given by a train of wheels connected with the drum, and carried to the 

 indicator. The first meter made on this principle was fixed up at the 

 extensive cotton mills of Messrs. Birley, Manchester, and had been working 

 almost a year and a half without the slightest disarrangement, measuring . 

 from 3-5,000 to 36,000 gallons per day. There was one with a twelve-inch 

 bore pipe now working, measuring the water supplied by the Corporation 

 of Manchester to the township of Dukinfield, to the satisfaction of both 

 parties concerned ; and there were as many as betwixt one and two hun- 

 dred meters working in various parts of the country. 



IRON COFFER DAM. 



In a report of the proceedings of a semi-annual meeting of the Corn- 

 wall Railway Company, in England, embracing the report of Mr. Brunnel, 

 the Engineer, on the works of the Saltash Bridge, on a part of the line of 

 unfinished railway between Truro and St. Anstell, we find a description 

 of a coffer dam of a novel construction, sunk in a very deep part of the 

 river, to facilitate the construction of a pier for the support of the centre 

 of the bridge which forms a necessary part of the line. The dam in ques- 

 tion is not only of a novel structure, but it is made to shut out water to a 

 greater depth than any other work for a similar purpose that we have before 

 seen any account of, viz. : a pressure, under high tides, of 70 to 80 feet. 

 It is so constructed as to act on the principle of the diving-bell, in case the 

 water should find its way into the inclosure. But it seems to have tlms 



