212 T. V. Holmes—Geology of Blackheath and Greenwich. 
The Lewisham and Blackheath Scientific Association (a then newly 
formed local scientific society) raised a fund from residents in the 
neighbourhood for the exploration of pit C, and appointed a committee 
to superintend the work.' From this committee an executive sub- 
committee was selected, consisting of Sir G. B. Airy, Dr. H. E. 
Armstrong, W. H. Bond, E. W. Brabrook, T. V. Holmes, H. W. 
Jackson, Rev. Brooke Lambert, da KG Laughton (chairman), Jk ae: 
Price, Dr. Prior Purvis, Rev. T. Wiltshire, and John Yeo. The hole 
was timbered and the work began. Ata depth of about 34 feet from 
the surface water appeared, and became more and more troublesome 
as the depth increased. From the report drawn up by the Chairman 
we learn :-— 
“The ground, which was continuously sand more or les mixed 
with water-worn rounded stones, varying in size from a marble to 
a cricket ball, was throughout broken and disturbed; it yielded 
readily to the spade, and “the pickaxe was at no time called into 
requisition. The earth behind the timber was thus all alive; it had 
no. cohesion of itself, and transmitted the pressure to the timbering’ 
almost as if it had been fluid. When the weight and liveliness of the: 
water was added to that of the sand this effect was intensified, and 
apprehensions began to be entertained lest the timbering should be 
found of insufficient strength.” 
At a depth of 43 feet there was an inequality of vertical resistance, 
which caused the timber framework to ‘cant’ and ‘long-corner.’ 
This tendency increased, and combined with the difficulty arisin @ from 
the inflow of water to stop further excavation, owing to the great 
difficulty and expense which would attend it. So it was resolved to 
drive an iron tube down, to test the hardness or softness of the 
material, and to ascertain the existence of any cavity. ‘Two tubes 
were driven down; the first was withdrawn after having sustained 
a fracture, the second was driven to a depth of 84 ft. 6 in., but was 
there stopped by some hard mass, which it could neither pierce 
nor thrust aside. The first pipe was easily drawn up; the second 
only with the utmost difficulty, though the track of each was almost: 
perfectly identical. As the second was being withdrawn specimens of 
the earth at the bottom were obtained by means of a small scoop 
attached to the end of a rod passed down the pipe, and these samples 
testified to the abnormal condition of the strata passed through. 
We read :—‘‘ Down to about 50 feet they are sandy ; but from that 
to the bottom are clayey, and more clayey as the depth increases. 
But a comparison with the known stratification of the district shows. 
that from 35 to 50 feet or thereabouts, is the level of the clayey beds ; 
that below that is the Thanet Sand; and it is therefore conjectured 
that the fine peculiarly greasy clay brought up by the scoop from the 
depth of 84 ft. 6in. may have been washed down when the shaft, 
no longer used, was suffered to fall in.” 
Accounts of subsidences in other districts, supposed to be analogous 
in some way to those at Blackheath, were sent in to the Committee, 
1 The Lewisham and Blackheath Scientific Association (like so many local scientific 
societies) was short-lived, and came to an end in 1893. Hence it seems desirable to. 
give a more detailed account of its work here than would otherwise be the case. 
