[65] These boilers are now much used for such purposes, they hold from 60 to 500 gallons and are light and portable; the temper of the bituminous mixture also remains uniform whilst being drawn off, and there is very little evaporation or waste arising from them.
[66] Since writing the above, the Liverpool and Manchester tram-road was designed I believe on this principle.
CHAPTER IX.
WOOD PAVING.
In the year 1843 Mr. Charles Cochrane, the President of the ‘Association for the promotion of Improved Street Paving, etc.,’ in a paper which he read before the Institution of Civil Engineers, on the State of the Streets of the Metropolis, said that there existed at that date 100,000 yards of wood pavement.[67] He further states that it is said to be slippery, but that he approves of it as the best material hitherto used, “both as regards its general economy and durability as well as its facility of traction, and more especially its extreme cleanliness.”
Two years previous to this date, Mr. Edward Lomas condemned wood pavement as slippery, and recommended granite pavement for horses with wood tram-tracks for the wheels of vehicles.[68]
Since these dates the question of wood paving has made giant strides, many companies and private firms having started business as wood paviors, with many various methods, which they strongly advocate as being superior to the others; amongst them I will enumerate and describe the following:
The Improved Wood Pavement Company.
—The ground being consolidated, a layer of sand is made the basis of the pavement, and assumes the shape the surface of the street is intended to take. Red-wood boards 1-inch in thickness are then laid across the roadway, from kerb to kerb, placed together so as to break joint; boards of the same material and thickness are then laid longitudinally, and breaking joint in the same manner.[69] On this foundation red-wood blocks are placed in rows, taking the same direction as the under flooring.
Between each row of blocks, a strip of wood ³⁄₄ × ³⁄₄ inch is nailed to the block and flooring, the blocks in all cases breaking joint; the spaces thus formed between the rows of blocks are then run with a thick composition which fills all vacant spaces there may be between the strip and the block, covering the strip about ¹⁄₈ of an inch. Gravel, dried and sifted through ³⁄₄-inch mesh, is then put in, solidly rammed, and composition poured in; the pavement is then covered to a depth of ¹⁄₂ an inch with dried gravel and composition for the purpose of indurating the surface, and filling the spaces flush with the top of the block, a slight covering of sand is then spread, when the traffic may immediately pass over.