162 C. W. DARLEY. 



Type H., Plate xvni. — This type includes large shallow rec- 

 tangular uncovered storage or settling tanks. 



No. 1 has brick walls built to a batter of one in six, and a 

 concrete floor lined with brick. This tank is used for storing and 

 settling river water before passing it on filter beds. 



No. 2 is built of concrete walls and floor and is used as a 

 combined settling tank and service reservoir, for this purpose it 

 has a central brick partition, so that one half may be cleaned 

 while the other half is in use — or one half may be filling from the 

 pumps, while in the other half the water is settling before it is 

 drawn off to the town. 



No. 3 is built with concrete sloping walls and concrete floor ; 

 the walls, or more properly speaking the lining, is laid on the 

 sides, which are formed to a slope of one-half to one. This class 

 of work is satisfactory only when the tank is wholly in excavation, 

 where any portion of the sides may be in embankment the 

 unequal settlement is sure to cause trouble and crack the concrete 

 lining. 



Where the lining has to be raised above the natural surface, it 

 is necessary either to construct a self supporting wall, or insert 

 frequent buttresses. 



No. 4 is constructed with side slopes of one and a half to one, 

 covered with scabbled stone pitching, laid dry, and a concrete 

 floor. 



Where the sides are in embankment, a puddle core-wall has 

 been constructed to make them water-tight. 



No. 5 is a large service reservoir excavated almost wholly in 

 sandstone rock. A thin floor of concrete has been laid to level 

 the surface, and any rents or joints in the rock were well guttered 

 out and filled with concrete. A portion of one side only had to 

 be raised with a concrete wall above the natural rock. Taking 

 into account the fact that there were practically no walls to 

 construct in this case, and no roof, the reservoir does not appear 

 to be very economical. 



