TESTING STONEWARE PIPES USED IN RETICULATION SEWERS. LVII. 



the pipes were taken. The whole of the expense incurred in 

 testing the pipes shall be borne solely by the contractor, and all 

 pipes injured or broken by the testing shall be immediately replaced 

 by sound pipes, subject to the foregoing tests at contractor's cost." 



Since November, 1896, the quantity of water that may be 

 absorbed has been increased to 4 per cent., that is if the pipe is 

 perfect in every other respect, viz., as to shape, glazing, etc., the 

 2 per cent, being retained if the parcel is not uniformly good on 

 outward examination. Great care is taken in choosing the sample 

 pipe from a parcel, to obtain one that to the eye represents a fair 

 average of the parcel. 



The crushing test is conducted with the machine already des- 

 cribed, under conditions that represent as nearly as possible, fair 

 working conditions when laid. Before fracture takes place, the 

 whole pipe is gradually pressed into the moist sand, so that it 

 takes a firm and uniform bearing. The fracture occurs suddenly, 

 in the form of a longitudinal crack along the top of the pipe from 

 end to end. 



The porosity test is then conducted as follows : — From the 

 broken pipe, two pieces are selected free from cracks produced, 

 during crushing, and without any glazed edge, one piece being 

 about 10 or 11 square inches in area, and the other 50 to 60 

 square inches. These pieces are dried in an oven, weighed, and 

 immersed in water for twenty-four hours. They are then taken 

 out, all superficial water is quickly wiped off, and the weights 

 again taken. The percentage increase in weight is then calculated. 

 The result of the porosity test depends to a large extent on the 

 area of the fractured edges as compared with the area of the glazed 

 portion of the tested sample. It also depends on the presence of 

 laminated cracks, due to imperfect drying before burning. In 

 practice it is found that the smaller pieces give the smaller increase 

 in weight. In the case of the smaller pieces, the proportion of 

 fractured edge to glazed portion is greater than in the large pieces, 

 and therefore the porosity might have been fairly expected to be 



