212 STABLES. 



proportion, say, of a shovelful of cement and a shovelful of 

 clean sharp sand to a bucketful of water), so as to bind the 

 stones together ; and work over the whole, cement mortar 

 (consisting of one part of cement and three parts of granite 

 chips of the size just mentioned) to a thickness of 4 in. 

 Before wetting the cement and chips, they should be 

 thoroughly mixed together with a shovel, so that the mortar 

 may be of uniform composition. The surface should be 

 worked over with a wooden float, and gutters and notches 

 made as may be required. The application of the mortar 

 should be done in one operation ; for if the upper layer be 

 subsequently put on, it might not adhere to the lower one, and 

 would consequently suffer a proportionate loss of strength. 

 Gutters may be conveniently made in the damp surface of the 

 concrete by placing in it metal pipes or metal rods sunk to half 

 their diameter and left until the mortar has become hard. 

 Notches may be cut with any convenient instrument. Only 

 slow-setting cement should be employed, for the quick-setting 

 kind is not so strong. The following is an extract from the 

 pamphlet published by the Rugby Portland Cement Company 

 on " Portland Cement " : " The cement mortar should be 

 used as quickly as possible after it is mixed, for to re-mix or 

 to disturb when partially set, destroys its setting property. 

 No doubt one of the difficulties attending the use of cement 

 mortar is the tendency on the part of the workmen to mix too 

 much at a time and afterwards to re-mix it. Or, secondly, to 

 mix it with too much water. This should be prevented, and 

 in order to secure satisfactory work must be attended to. For 

 cement will not bear working up like lime mortar, the great 

 essential of its success being that it should be gauged, laid in 

 position, and left at rest in as short a time as possible. It 

 should be allowed to dry naturally, artificial heat being in- 

 jurious." The cost of good Portland cement is about 

 2 I os. a ton, and that of granite chips, exclusive of 



