WATER SUPPLY TO SYDNEY BY GRAVITATION. J 10 



inches. The length is 226 feet, and it is curved up stream, the 

 front face being convex, to a radius of 300 feet. There are two 

 valve houses, also built of concrete. 



The dam is perfectly tight, and this is due to the extreme care 

 taken by Mr. Dobson, the eugineer, and Mr. Brown, the inspector 

 in charge, with the testing of the cement and the mixing of the 

 concrete. It was constructed by day labour, with the exception 

 of the coping. The concrete was put in in 7-inch courses, and 

 well rammed. It cost £3 8s. per cubic yard, including every 

 expense except the engineer's salary. The total cost was £17,306 

 12s. Labourers were paid 6s. 6d., masons 10s., and plasterers 8s. 

 per day. Cement cost 31s. per barrel. The outlet pipes are of 

 cast iron, bedded in the concrete. The work was begun in January, 

 1873, and finished up to the coping in June, 1874. The reservoir 

 contains 141 million gallons, so that the cost of storing is £122 

 15s. per million gallons. The rock on which it is built is sand- 

 stone, but slate with quartz leaders appears in the creek bed, and 

 there the stone was much crushed, which necessitated a greater 

 depth for the foundations than was anticipated." 



[Three plans.] 



