50 PROTECTION OF WOODLANDS. 



the shallower and narrower feeders which lead into the latter, are 

 regulated by the nature of the soil, and depend mainly on its 

 greater or less degree of wetness. 



The execution of drainage works should be carried out at the 

 driest time of the year, during late summer or in autumn, work 

 being begun with the main drain and at the lowest level, and 

 gradually working upwards towards the higher levels, as other- 

 wise work would be interfered with by the water descending in 

 the drains as they were being formed. The earth removed from 

 the drains and ditches should be thrown out on either side ; for if 

 merely banked up at the edges, it might easily be washed back 

 again into the ditches by heavy rain. 



When once formed, the ditches must be kept clean and in 

 good condition as long as necessary, reeds and other aquatic 

 weeds being cleared away, earth that has been washed in being 

 dredged out, and any damage to the scarps repaired. It may not 

 infrequently be observed that areas, which, when unwooded, have 

 an excessive quantity of moisture, gradually get rid of this 

 through the crops imbibing larger volumes of water for trans- 

 piration through the foliage as they grow older, and in such 

 cases the retention of the drainage ditches has no longer any 

 object, so that they can be left to choke and fill up. 



Open ditches are certainly the cheapest means of drainage for 

 temporary requirements, but they are easily damaged in 

 ways by rain, frost, &c., as well as by cattle and by men ; the 

 are also apt to interfere somewhat with communications, and 

 especially with the extraction of timber, besides necessitating 

 frequent outlay for repairs. Instead of such, therefore, covered 

 drains constructed with stones, fagots, or brushwood, are also 

 occasionally formed. The ditches dug are, for the most 

 filled up with fascines or bundles of brushwood on which 

 layer of moss or turf is laid, and then earth is piled over this ; tl 

 interstices between the brushwood, which remains undecomposed 

 for a number of years, form the channels through which the 

 water percolates, and suffice for a merely moderate and often the 

 most advantageous degree of drainage. 



On account of the greater cost involved, the filling up of tl 

 drains with stones in place of brushwood takes place 1( 

 frequently ; it depends for the most part on whether tl 

 necessary material can be found in the immediate vicinity, 



