1886.] Van Wi/k's Vlci Reservoir. 225 



As all made-banks are liable to settle down more or less, the top 

 as finished was kept higher than the normal level, by one half-inch 

 for every foot of vertical height. 



A coating of 3 inches of gravel was spread over the top of the 

 bank to protect it from rain, and the trampling of cattle and sheep ; 

 and along the edge of the inside slope a dry stone wall 2 feet wide 

 by 2 feet high was built as a protection from spray, &c. 



The w^ater is led from the reservoir to the main farrow, by means 

 ,of two iron pipes, one of 20 inches in diameter and the other 12 

 inches. These pipes pass through a culvert made of concrete 4 feet 

 wide by 6 feet high, which is built in the solid ground in the kopje 

 which forms the east abutment of the embankment. At the reservoir 

 end of the culvert is built a stone tower, in cement mortar, 33 feet high^ 

 with an external diameter at the base of 13 feet, and at the top 10 

 feet ; the internal diameter being 5 feet. This tower is for the purpose 

 of working the different valves, of which there are five in all, each 

 of the two pipes being pro voided with two, a shuttle valve on the 

 outside, and an ordinary one in the inside of the tower. 



The fifth valve is a 6-inch one to be used for any water which may 

 collect in the tower. Access is obtained to the top and inside of the 

 tower, for working the valves, and for making repairs, by means of 

 iron steps built into the masonry. 



The top of the tower is covered with cast-iron plates, resting on the 

 walls and on the channel irons, which support the pillars through 

 which the valve rods pass. 



The 20-inch pipe passes through the base of the tower, its centre 

 being nearly 26 feet below the highest water level. It is then laid 

 on the floor of the culvert, extending as far as the plug wall, or as far 

 as the puddle core of the embankment. 



The 12-inch pipe draws water from the reservoir at a point 13j 

 feet below the highest water level, passes down through the tower 

 into the culvert, where it rests on brackets supported on short iron 

 columns, at a height of 3^ feet above the floor. 



At intervals of 9 feet along the top of the culvert, masonry rings, 

 set in cement mortar, 2 feet wide and 1 foot thick, were built to 

 arrest as much as possible any percolation of water, and so that the 

 earthwork and puddle of the bank should join firmly with the 

 masonry. The filling in of the space between the top of the arch and 

 the surface of the ground was carefully done. A layer of ground was 

 first put in and thoroughly soaked with water, well trampled and 



