ASPHALTE is a name given to various bituminous compounds, which have been much used of late for street-pavements, for the platforms of railway stations, and for flooring, roofing, and protecting buildings in various ways from damp. One of the most important of these is the Seyssel asphalte, introduced into this country by Mr. Claridge, under a patent obtained in 1837.
The principal ingredient of tho asphaltic mastic of Seyssel is a dark brown bituminous limestone, found near the Jura Mountains. This stone is broken to powder and mixed with mineral tar, when intended for fine work, such as the covering of roofs and arches, the lining of tanks, and application as cement ; or, when intended for the coarser purposes of pavement and flooring, with mineral tar and sea-grit ; and the whole is exposed for several, hours to a strong heat, in large caldrons, until the ingredients, which are continually stirred by machinery, are perfectly united. The mastic is then run into moulds so as to form it into large cakes or blocks, which are broken up and re-melted on the spot in portable cal drons, with wood or coke fires, with the addi tion of a little more mineral tar ; the whole being well stirred to prevent burning, and to ensure the perfect mixture of the ingredients. When ready for use the mastic emits jets of light smoke, and drops freely from the stirring instrument. It should then be carried very quickly to the spot where it is to he applied, in iron ladles or heated iron buckets. In all
cases, however, it is desirable to have the cal dron as close to the work as possible ; and in covering brick arches or arched roofs, it may be hoisted to the top of the building, proper precautions being observed to shelter the finished work from injury.
Pavements of asphalte are laid upon a firm and dry foundation of concrete ; and in laying the asphalto the surface is divided by slips of wood, which serve as gauges to regulate the thickness, into compartments of about thirty inches wide, in which the hot cement is spread and levelled with wooden instruments ; after which, while the surface is yet soft, sand mixed with slate dust, dead plaster of Paris, or pow dered chalk, or, for coarser work, clean sharp grit is sifted over it, and rubbed or beaten in. The thickness of asphalte used for pavements varies from half an inch to about an inch and a quarter ; from half an inch to five-eighths is sufficient for roofs and the covering of arches to prevent the filtration of water, and for the lining of' tanks and ponds ; and about half that thickness is sufficient for covering the ground-line of brickwork, to prevent the rising of damp.
The experience of the last few years has shown that asphalt° is neither a pleasant nor a profitable material for the pavements of the London streets.