MECHANICAL PREPARATION OF SOILS. 



41 



D/ 





i 



io6. Having surveyed and mapped out tWs area, which may be done 

 either by means of the theodolite, or by 

 a spirit-level and actual measurement, it 

 ■will be found to contain a small valley 

 ranging from north to south, surrounded 

 on three sides by gently-rising ground. 

 The bed of the valley is a stiff clay, and 

 somewhat marshy, from the overflowing 

 of the brook which occupies its eastern 

 extremity. The heights to the east 

 range away for about 1,000 feet to 

 the north, the summit being a bed of 

 gravel, which crops out, and joins the 

 clay at the line indicated in the drain, 

 M 2. On the rising ground to the north 

 a small pond or lake collects the waters 

 from the surrounding gravel-beds, and 

 has retained them until they have forced 

 their way into the valley. Two gentle 

 elevations, with a depression between 

 them, occupy the west, an ancient pas- 

 ture-ground, that best of all material for 

 forming a garden. To the south the 

 land falls off gently to the bed of the 

 river, which flows from west to east, 

 some half a mile distant. 



PLAN AND CBOSS SECTION A A. 



Having mapped out the area, we find that it contains about 1,000 

 ranging towards the ,- ,. „„ 



107 



feet, 



north and north-west, the 

 mouth of the vallej^, where 

 it opens out towards the 

 river, being about 400 feet 

 wide, the country falling in 

 undulating scenery beyond, 



m/ 



PEOFILE OK WEST HILL. 



In order to secure the thorough drainage of 

 this site, a deep main drain, ]\I 2, must run from the foot of the northern 

 heights to another main drain, M 4, intersecting it at the lower part of the 

 valley, and cai-rying the accumulated waters into the brook lying to the east. 

 These two drains are, of course, the key to the whole system, and should either 

 be barrel-drains or pipe-drains of the largest size, fitted in with glazed pipes 

 properly jointed, with socket-joints and elbow-joints to receive the lateral drains. 

 The size and kind of drains, however, should be matter of very exact calculation, 

 based on the average fall of rain in the neighbourhood, and the arrangements 

 for securing the house sewage within the grounds. Nothing but the overflow 

 should be sufiered to escape through these drains ; but they must be of 

 sufficient size to provide for any possible fall of water. 



