Proceedings. 73 



been found, and a good many were discovered after some 

 careful digging by various members of our party. Many^ 

 oyster- shells are also to be found, mostly lying detached, thus 

 indicating that they had lived on a still bottom. This bed of 

 Greensand is about sixteen feet in thickness, and at the top 

 of it is a band about eighteen inches thick of very hard 

 lavender-coloured concrete, composed of pebbles and shells. 

 Above this are seen the beautifully- coloured clays of the 

 Woolwich and Eeading series, the lowest bright yellow, then 

 green, j)urple, and dark blue, almost black. All these colours 

 are not, however, displayed in this cutting ; as the strata dip 

 considerably to the north, we have to proceed some distance 

 further in that direction before reaching the uppermost beds ; 

 this soon brings us to a tunnel one-third of a mile long, from 

 which the excavations consist chiefly of the purple and dark- 

 blue clays. It was then being excavated through several 

 shafts, the borings not having yet begun from either end. 

 Several of the party descended one of these shafts, and were 

 much interested in seeing the work of digging, propping, and 

 building up the brickwork going on. Timbers of great size 

 and strength were required to support the roof, and new ones 

 had to be continually advanced and carefully wedged in their 

 positions as the length of the boring was increased. We were 

 told that after the brickwork is all built up it requires to be 

 still propped for about three weeks, when it is completely set, 

 and the supports are removed. Still, with all precautions, 

 these stiff plastic clays are very dangerous to work in, and 

 several accidents have occurred. (Since the time of om- visit 

 the tunnel has fallen in, by which the progress of the railway 

 has been much retarded). In the cutting at the north end of 

 the tunnel the dark clays are the lowest series exposed ; the 

 top bed of these is intensely black. Above these occur the 

 Oldhaven Sands, pale in colour, which extend along the 

 whole of the remainder of this cutting. The entire thickness 

 of this stratum is about twenty-seven feet. At the base, 

 immediately above the black clay, is a very hard bed composed 

 of shells and pebbles. The whole of the various interesting 

 strata so excellently displayed in these cuttings were pointed 



