122 



F. M. GUMMOW. 



wetness showed, which, however, gradually " took up ,f 

 within two to three months. 



A concrete-iron pipe 9*84 feet long, 1 foot 8 inches 

 diameter, and If inch thick, taken from a pipe line, having 

 been three years in use, uuder a working pressure of 59 

 feet, showed no wet spots until subjected to a head of water 

 of 125 feet. Upon being re-tested later on, it withstood a 

 pressure of 130 feet head for one month without sweating, 

 and percolation only commenced under a head of 197 feet. 

 Numerous instances of the extensive use of concrete-iron 

 pipes couid be mentioned, among which area length of four 

 miles of 2 feet 7} inches diameter pipes, 1-J inch thick, 

 working under a head of 23 feet, for the City of Venice; 

 18', in ilcs of 2 feet diameter pipes in Algeria, under a head 

 of from 56 feet to 78 feet, with thickness varying from 1*6 

 inch to 1*8 inch ; 3| miles of 2 feet diameter pipes at 

 Valence, under a head of 05 feet of water; 38 miles of 2 

 liameter pipes in Tunis, etc. 



In New Smith Wales concrete-iron pipes to withstand 

 internal pressures have so far only been manufactured in 

 connection with tlieir application as bridge cylinders. The 

 cylinders were designed to withstand an internal pressure 

 of 50 feet head of water, and have been successfully sunk 

 in many places with and without the airlock. They are 

 manufactured in 3 feet 6 inches to 6 feet diameters, and 

 contain within their thickness longitudinal steel bar con- 

 nections, which are coupled — in jointing the cylinders — 

 by means of fishplates and wedges. 



Regarding local tests of the impermeability of pipes under 

 high internal pressures, the author made a series of tests 

 with the ordinary concrete-iron pipes, which had been 

 manufactured for use as culverts, stormwater channels, 

 etc., and not designed to withstand internal pressures, and 

 found that they withstood pressures up to 110 feet head 



