Chap. IX.] AVENUES AND BOULEVARDS. 145 



may be known by the mastic dropping freely off the stirrer, and 

 by jets of light smoke darting out of the mixture — it is conveyed 

 quickly to the spot where it is to be used, in heated iron buckets 

 or ladles. The cauldron ought to be as close to the work as 

 possible, and in covering brick arches it should be hoisted to the 

 top of the building. It must be clearly understood that the only 

 kind of bitumen to be used is that impregnating the limestone 

 itself. 



In forming foot or carriage ways it is most important to secure 

 a good foundation by removing or ramming the soft earth, and 

 laying a course of concrete, care being taken to allow the whole 

 to dry before putting down the asphalte. If this precaution is 

 not attended to, the heat will convert the moisture in the concrete 

 into steam, and fill the asphalte full of airholes and bubbles. The 

 thickness of the layer of asphalte may be regulated by slips of 

 wood arranged across the pavement at a distance of 30 inches 

 from each other— a width quite sufiicient for one man to work at 

 a time. If two men are employed, double the width may be 

 taken, as it is always better to have as few joints as possible. 

 The work is levelled with a long ciirved wooden spatula, assisted 

 by a long straight ruler, which stretches across the layer of 

 asphalte, over which it is moved backwards and forwcards, the 

 wooden gauges supporting its ends. If the surface is intended to 

 be smooth, a mixture of equal parts of silver-sand and slate-dust 

 or plaster of Paris is sifted over it before it has quite set, and 

 rubl)ed down with a flat tool of wood. If it is required to be 

 rough, sharp grit is to be beaten in with a heavy wooden block. 

 One portion of the pavement being complete, it is best to proceed 

 to lay the next but one, leaving the intermediate space to be 

 filled up afterwards, when the first layer is firm and cold, so as 

 to insure a good joint. 



The thickness of asphalte for footways varies from half an inch 

 to an inch and a quarter, the former being sufficient for common 

 floors and courtyards, the latter for carriage-pavements. A 

 thickness of from half an inch to five-eighths is sufficient for 

 roofs and the coverings of arches, and for lining tanks and ponds, 

 and about half an inch for the ground line of brickwork to 

 prevent the damp from rising. An asphalted surface admits of 

 easy repair. By placing hot mastic on the places requiring it, 



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