LAMPLUGH : THE FLAMB0R0UGH DRAINAGE SECTIONS. 
147 
From this point the trenches, from 13 to 17 feet deep, reached 
the chalk almost uninterruptedly throughout the whole length of 
Tower Street. Its surface was, however, very irregular, occasionally 
rising and sinking suddenly from within 5 feet of the road level to a 
depth of 12 feet or more. The drift deposits, still consisting in their 
lower part of sandy material with tough red clay above, filled up all 
these inequalities and presented a level surface. 
The first short branch which passed out from Tower Street on the 
right did not reach the chalk in a depth of 14 feet,, and showed a 
rapid thickening in that direction of the gravelly portion of the drift. 
The shallow branch to the left, 5 to 10 feet deep, along Carter 
Lane on the other hand, reached the chalk after passing through 
only three or four feet of red boulder clay, thus proving the rapid 
attenuation of the glacial beds in that direction. The clay in this 
section contained many large boulders of basalt, sandstone, carbon- 
iferous limestone, etc. 
The main drain turns sharply to the right through Cross Street. 
Here the chalk sank gradually out of reach, and the drifts pro- 
portionately thickened. 
In the southern part of North Street the trenches, 15 feet deep, 
were filled in before I had an opportunity to examine them, but they 
have been described to me as consisting of an irregular mixture of 
boulder clay and sandy gravel, the different patches of gravel varying 
much in appearance, as is so commonly the case in these deposits. 
The two shallow branches to the right, along Allison Lane and 
through School House Lane (both ending with a depth of five feet), 
passed through the red Upper Boulder Clay into stratified beds of 
drift beneath it, and in both instances in going eastward the clay 
disappeared, and gave place to rough clayey water-yielding gravels. 
Following the main drain, one of the deepest portions of the 
trenches was reached at the corner near the "Rose and Crown," 
where a branch leads off to the north side of the North Mere. 
Here the excavation was carried to a depth of 16^ feet, and was 
wholly in the glacial deposits. The lowest bed was a mass of very 
dark earthy boulder clay containing many small pebbles of chalk. 
It resembled in every respect the Basement Clay of the cliff sections, 
