98 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



experiments was satisfactory in every way ; inasmuch as before, an 

 18-inch pump was required to be constantly at work to keep the 

 water down, whilst afterwards only one hour's pumping was 

 necessary in about 40 hours. 1 



The following course was pursued by Mr. J. Kingston, C.E., 

 in constructing a large sea-sluice at the River Glen Outfall, in 

 1879. In this case the foundations were in quicksand; the 

 aprons and floors were constructed of 3f -inch Memel planks laid 

 on whole timbers, and secured to them with treenails and spikes, 

 whilst, under the planking and surrounding the timbers, there 

 was 3 feet of concrete. Before laying the planks, every care 

 was taken to render the surface of the concrete with Portland- 

 cement mortar. It was discovered that the act of driving 

 the spikes and treenails had a tendency to shake the 

 mortar away from the under side of the planks, causing 

 thereby leaks to appear. As an experiment, a hole was 

 bored in the floor, and a stand-pipe about 8 feet long 

 inserted, and to the top of which a small hopper was fixed; 

 Portland-cement grout was then poured in, which diffused itself 

 under the floor. A small force-pump connected with a tub for 

 containing the grout was then prepared, and the grout was 

 pumped under the floor with a heavy pressure, until every 

 fissure or space was filled, and the whole of the floor made 

 absolutely water-tight. 



In executing some extensive repairs to a large sea-sluice, 

 much the same course was followed by the same engineer. In 

 this case, the foundations were in quick silt, the sill being 6 

 feet below low water in the river with a tidal rise of 20 feet. 

 The oak planking of the entrance was taken up, and about 

 3 feet of concrete was got in and brought to within about J 

 of an inch of the top of the horizontal timbers. The concrete 

 set very satisfactorily, but, owing to the head at high water, 

 it was impossible to prevent the upward filtration of water 

 from the silty subsoil, and, consequently, the percolation of 

 water between the concrete and the floor timbers. No attempt 

 was therefore made to render the surface of the concrete before 

 laying the planking ; the constant streaming of the water would 

 have rendered such a course useless. The 3f-inch Memel 

 planking was therefore laid on the whole timbers, and secured in 

 the usual way with treenails and spikes with a full of an inch 



1 Engineering. 



