[62] The usual specifications for the Guidet paving blocks (in New York) require that they shall be of granite, equal in hardness to the Quincy granite, of durable and uniform quality, each measuring not less than 3¹⁄₂ nor more than 4¹⁄₂ inches in width on the upper surface or face, and not less than 10 nor more than 15 inches in length, and not less than 8 nor more than 9 inches in depth. Blocks of 3¹⁄₂ inches in width on the face to be not less than 3 inches in width at the base; all other blocks to measure on the base not more than 1 inch less in width or in length than on the face. The blocks are set upright in close contact on their edges in courses, with the longest dimensions and the continuous joints running across the street, breaking joints lengthwise of the street. The ends of the blocks are dressed off so as to give close joints in the direction of the draught, while the broad vertical sides of the blocks are left rugged or uneven, or with the split rock-face so that the continuous joints running across the street are somewhat open. _Vide_ ‘Roads, Streets, and Pavements’ by Q. A. Gillmore, p. 157. [63] _Vide_ ‘A Treatise on Roads,’ by Sir Henry Parnell, p. 130. [64] As these ingredients often vary very much in their constitution, the surveyor must use his judgment to a great extent as to these proportions. [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: