Wool Hat Making

1887 Scientific American  
Chelsea, between l{a1'lborough Road and Keppel tions are being made for a cement that will not leave Street on the nortb side, a len�th was laid in 1885 on a a residue of 10 per cent. on a 76 mesh. The weight 3 inch concrete foundation, which was covered with runs from 116 to 120 lb. per striked bushel. Before use, mastic asphalt 7,4; inch in thickness. On this % inch the cement is laid out to cool fourteen days, and is of compressed asphalt is laid. The mastic asphalt turned over frequently in
more » ... over frequently in that time. Great care is was laid to absorb by its elasticity the movement of taken to keep the direct rays of the sun off the cement. the concrete without transmitting it to the compressed The company exposed part of a sample of cement to asphalt. It has survived two winters of great severity, the sun, and exposed the other part to the air. It was and has lived twenty-one months without> , any cracks ap-found that the part exposed to the sun showed a loss pearing. From this it would appear that the principle of strength equal to 50 per cent. The soluble silica of a material between the concrete and the compressed used for the induration of the stone is a clear viscous asphalt which will absorb the effects of the move-substance made from pure flint and caustic soda, Illent� of the concrete is a correct one, and the writer which are digested by heat under pressure in Papin's invites the members of the association to experiment digester or an analogous lllachine. Its strength is on cheapening the method. The present result is an technically known as 140° Twaddell, which shows 1,700 increase of life of 33 per cent., at an increase of cost of on a hydrometer. The silica is diluted with water 12 per cent. until it shows 1,250 or 1,300 on the hydrometer, and is As evidence of the durability of compre8sed asphalt then a clear copper-colored liquid. !n footways, those in Cheapside ma l be named. They The stone is made of three parts by measure of were laid in 1876, at a thickness of inch, and are now washed granite and one part of cement. 'I'hey are wearing through. On the south side of the Strand, thoroughly incorporated in a dry state in a horizontal east of Wellington Street, I inch of compressed as�halt cylinder by machmery. and when this is secured, water was laid in 1881, and has had only the most trIfling is sparingly added, and the mixing continued. At each repairs. The streets in the City, with the heaviest foot mixing there is made sufficient concrete for a 3 foot by traffics in the world, are paved with compressed 2 foot by 2 inch slab only. When it is ready for putting asphalt on the footways. The advantages of asphalt 'in the mould, the concrete does not appear to the eye foot pavements are durability, a smooth surface un-to be sufficiently wet. The moulds are metal lined, true broken with joint"" a good foothold, even and regular in shape, with clearly defined arrises. Before the con wear, their impervious character, and the readiness crete is placed into them they are oiled all over, and and neatness with which they are repaired. They then placed on a trembler. This is a machine which have a somber appearance, and. show water on their gives a rapid vertical jolting motion to the mould. surface longer than stone pavements. They wear to When the machine is started, the concrete is placed the last thickness without breaking up, and give a into the mould by small shovelfuls at a time, and two useful wear for the whole of their thickness. 'Vhen a men with trowels spread it over the mould. When stone or othel pavement has worn 1 inch, it may not be the mould is filled they pat the concrete with the half worn through, but its useful life is over. Where trowels, the water rises to the surface, and an even, there are cellars under foot ways, asphalt as a material smooth face is secured. The mould and concrete are for foot ways is unrivaled. In ordinary traffics, such then removed to a rest for two days. The whole opera as those named in King's Road (7,000 to 8,000 persons tion of mixing the concrete and making the slab in the per day), an asphalt pavement can be lain 1 inch mould is completed in six minutes. Machine-made thick, with the certainty that for at least ten years it stones are of necessity homogeneous, as veneering is will need no repairs whatever. This pavement has impossible during the process. The slabs, when taken also the advantage that the foundation is always,pre-from the moulds at the end of the two days, are air served and good for use again when the wearing sur-dried for seven or nine days, and then immersed in a face of asphalt has to be renewed. The following silica bath for seven or nine days more. They are then abstract of the present contract schedule in Chelsea stacked in the open for some months before use. The will give the prices for these pavements: value of the silica bath is in hastening the hardening of Per sq. yd. the stone. At the end of a month the stone will stand Compressed or mastic asphalt 1 inch in s. d. from 30 to 40 per cent. more tensile strain if silicated than thickness on 3 inches of concrete ... . 6 3 if air-dried only. It is dOUbted by Mr. Faija whether
doi:10.1038/scientificamerican12311887-9996supp fatcat:pzjecaxshfhkhcqworbxvltyxa