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POPULAR SCIENCE REVIEW. 
was found, on discovery, to have been used for a considerable 
time as a cesspool. The existence of both shaft and chamber 
was unknown to Mr. Jackson, the present proprietor of Eltham 
Park, till their discovery at the end of a disused drain by a 
workman sent along the drain to find out the course taken by a 
quantity of water that had escaped through a leakage. Mr. 
Petrie notices that five courses of chalk occur in the shaft in 
the midst of the brickwork, about 47 feet from the surface, and 
remarks that the chalk for these courses was no doubt procured 
from the chalk in the shaft 70 feet below, which must have 
been unlined at the time from these chalk courses downwards. 
It seems to me most likely that the shaft was first lined when 
the chamber below was utilized as a cesspool, and that it is 
impossible that the latter could have been originally constructed 
for that purpose. 
It will be evident that the Danes’ Holes mentioned differ 
from the other classes of pits in the Chalk not merely in 
details of construction, but in geological position. For the 
others are sunk where chalk is at or close to the surface, 
as at Grime’s Graves, or in brickyards, as at Shooter’s 
Hill. But though pits of the Danes’-Hole class are not ne- 
cessarily found on any one particular horizon, a little con- 
sideration shows that the pits at Joyden’s Wood, Eltham, and 
Charlton Park cannot have been intended as pits for cJialk or 
flint. East of Joyden’s Wood is a broad suread of bare chalk, 
yet the makers of the pits there have preferred to go through 
40 to 50 feet of Thanet Sand in addition ; while Eltham Park, j 
Charlton Park, and Blackheath, all stand on the Blackheath 
Pebble Beds, and could never have been the sites of brick or 
tile works. In addition, there is plenty of chalk near at hand, 
both at Charlton and Blackheath, north and west of the 
plateau. 
Thus by a process of elimination ending in the ‘ survival of 
the fittest,’ pits of the Danes’-Hole class remain as the only 
probable explanation of the Blackheath subsidences. A little 
consideration will show that the inconvenience as regards the 
water at 34 feet, which was so serious a matter to us, with our 
large shaft and shattered ground, would not be very formidable I 
to men sinking a shaft of 2 feet 9 inches in unbroken material, j 
A relative who has seen much of primitive mining in Bolivia I 
at once suggested to me that they would soon stop the per- 
colation of the water by claying the sides for the two or three 
feet in which such protection was necessary. The pebble 
beds would probably stand very well in the shaft if subject 
only to the gentle percolation of water, and shielded from the 
direct action of rain. Of course a shaft in such strata would be 
ascended and descended by means of a notched tree-trunk, or 
