THEORY AND PRACTICE OF CONCRETE-IRON CONSTRUCTIONS. ] 23 



of water before sweating or cracking. The pipes tested 

 varied from 12 inches to 30 inches in diameter, and from 1\ 

 inches to If inches in thickness. As these tests were made 

 primarily with the object of ascertaining the bursting 

 strength of the pipe, and extended in each case only over 

 a short period, the tests cannot be regarded as a true gauge 

 for imperviousness to sweating, for to ascertain that it 

 would have been necessary to extend the period of the test 

 pressure over a considerable time. With regard to the 

 second type mentioned, these can be made to withstand 

 any internal pressures required similarly to steel pipes. 



Before concluding this portion of the paper it is advis- 

 able to draw attention to the necessity which has arisen 

 in Europe and America to issue regulations in order to fix 

 a standard of the materials to be used, the stresses admis- 

 sible and the method of carrying out and testing these 

 constructions in order to safeguard the public against their 

 indiscriminate use by those not qualified to design or con- 

 struct. This step became necessary on account of the 

 many accidents in connection with these constructions. 



* * * 



Particulars of a test of a plate-beam construction made 

 on a large scale in this State being available, and this form 

 of construction coming more and more into general use, a 

 description of the construction and the test of same should 

 be of interest. By instructions of the fingineer-in-Chief 

 for Existing Lines, N. S. Wales Railways, a concrete-iron 

 plate-beam construction was built in order to ascertain its 

 strength and carrying capacity. The site chosen in the 

 Newcastle Railway yard had an old concrete floor, and as 

 the foundation soil in that locality was rather uncertain, it 

 was deemed advisable not to disturb the same, but to build 

 the construction on this floor. In order to distribute the 

 pressure of the piers over as large an area as possible, four 



