10 Aug., 1918.] Apple Culture in Victoria. 455 



grade where necessary. Then the whole of the exposed surface of the 

 sub-soil should be ploughed and the portion from the excavation scooped 

 up into position to form the embankment. The objective in ploughing 

 the portion supporting the embankment is to create a rough surface and 

 thus subsequently form, at this point, a combination of the retentive 

 soil particles which prevents seepage from the dam. 



The chief factors to be taken into account when calculating the width 

 of the base of the embankment at the sub-soil level are the nature of 

 the clay to be used in the construction of the bank, the extent of the 

 surface area of the water to be stored, and the depth at its maximum 

 level. When these matters have received consideration, and an esti- 

 mate has been made of the volume of water, care should be taken that 

 the embankment be of ample proportions to contain it, thus obviating 

 possible necessary reinforcement later. 



The clay in many instances loses its cohesiveness through the action 

 oif the air while the water is at the lower levels, and if the embankment 

 be too steep the earth is washed in by the rippling of the surface water 

 caused by the wind when the higher levels are reached. To guard 

 against this contingency and maintain the maximum holding capacity 

 of the dam, the inside batter of the embankment should be at an angle 

 of about 45 degrees. This detail in construction should always be con- 

 sidered, but more (particularly when the surface area of the water is to 

 be extensive, and the situation of the dam is exposed to prevailing 

 winds. 



The one-horse scoop, with a capacity capable of shifting about J cubic 

 yard of earth, is employed to transfer the clay from the excavation to 

 the embankment after each successive ploughing of the bottom vmtil the 

 desired depth is reached. The number of these scoops used in making a 

 dam varies according to the size of same and the time limit allowed for 

 its completion, but generally from three to six are employed. The one- 

 horse scoop, being made of light material, easily drawn, and on account 

 of the freedom with which it may be manipulated, is now almost 

 exclusively employed for this work in preference to the larger two- 

 horse scoop. 



Plate 172 illustrates a section of a dam, with the water at its maxi- 

 mum level, and shows the formation of the embankment with the 2-inch 

 outlet pipe in position. This pipe should be placed as shown, before the 

 .building of the embankment is commenced. The intake end of the pipe 

 in the dam should be fitted with an L piece or the end of the pipe may 

 be bent upwards as shown, to prevent the admission of silt, the aperture 

 ■being covered with galvanized wire netting of fine mesh to exclude 

 debris. Should it be desired to irrigate portions of land on either side, 

 at a higher level than the outlet pipe, but below the level of the water 

 in the dam, this may be accomplished by attaching a hose to the pipe 

 and conducting the water to the situation where needed. The water 

 from catchments of this kind, however, is almost invariably used for 

 irrigating the land below the level of tlie outlet pipe. 



It will be seen that the constructing of a dam on a slope is a rather 

 simple proposition, and it will also be observed that in this case the 

 water is both accumulated and distributed by gravitation. But diffi- 

 "culty is often experienced in inaugurating a scheme for the irrigation 

 of an orchard occupying the summit of a ridge or rise when the area of 

 the elevated portion is not sufficiently extensive to afford adequate 

 catchment. To meet this emergency and provide sufficient water with 



