104 



Geology of the Keytliorpe Estate. 



ing an estate the presence or absence of these natural furrows 

 between the warp-drift and the substratum should be determined 

 by numerous trial-holes, as well as their average depth and 

 direction. They will generally be found on land with a con- 

 siderable fall, and they will run in most cases — though I have 

 seen exceptions — in the direction of the fall. 



In making these trial-holes the principal expense attending 

 the construction of a map of the soils, subsoils, and substrata of 

 an estate will be incurred. It will, therefore, be good economy 

 to record this information on a map — and there are few estates 

 without one, or for which one cannot be obtained from the Tithe 

 Survey Office. It has so long been the custom with agriculture 

 not to look below the surface, and with geology to look only at 

 the substrata, that there are, I believe, few estates, even those 

 whose resources are best developed, on which such a systematic 

 investigation of the superficial deposits and of the mineral cha- 

 racter of the substrata, would not bring to light some hitherto 

 neglected mineral manure, or some bed of stone, clay, brick- 

 earth, or gravel, having an economical value which would repay 

 many times over the trifling expense which would be incurred 

 by such a survey. 



WilminQton, near Dartford, 

 Nov. \, 1852. 



Postscript. 



Since the preceding pages were in the press, Lord Berners has kindly furnished 

 me with an account of the total cost of draining 398f acres. The expenditure 

 for labour appears, by this account, to have been 632/. For this sum there 

 were cut 103,981 yards of drains, of various depths, in the following propor- 

 tions : — 



Yards. 



3-feet drains . . . . 23,678 



3^ 



4 



4i 



6 

 7 



1* 



23,812 

 43,579 

 642 

 192 

 354 

 240 

 11,484 



103,981 



This gives 311,943 pipes of a foot long, which may be called, for round 

 numbers, 312,000. Having no data from which to ascertain the proportions 

 of 1^ and 3-inch pipes used, I assume half of them to have been 3-inch pipes, 

 which must be considerably above the truth, and therefore unfavourable to the 

 Keythorpe system. 



