Manchester Memoirs, Vol. Ixii. (1918), No. 11. 7 



by about 3 feet of clay only. Between Light Oaks Road and Weaste 

 various exposures show sandy Drift with lenticular beds of sandy 

 marl. 



These sections prove that the Glacial sands are absent in the 

 areas surrounding the main outcrop ; it may therefore be assumed 

 that the sands form a huge lenticular patch, thinning out on all 

 sides. It is true that the actual thinning is seen in one place only — 

 that is in the Rochdale Road set of sewer sections, of which there are 

 eight in a distance of a little over a mile. The first of these gives 60 

 feet of sand overlying clay, the second 59 feet of clay over more than 

 30 feet of sand, the third 56 feet of clay over more than 31 feet of 

 sand, the fourth 66 feet of clay over 73 feet of sand, the sixth 87 feet 

 of clay over more than 59 feet of sand, the seventh 81 feet of clay 

 over 7 feet of sand, the eighth clay only. The first of these sections 

 shows sand over clay, but, as the base of the clay is not reached, this 

 may be only a lenticular band. 



In spite of the fact that this is the only set of sections in which 

 the actual disappearance of the sand can be followed in detail, the 

 rapidity with which the sands disappear by Alms Hill, Light Oaks 

 Road, Boggart Hole Clough, Heaton Park and the sections beyond 

 these areas shows that there is replacement of sand by clay. This 

 seems to show that the sands of Kersall Moor occur as a lenticular 

 patch, and not as a definite layer under or overlying the neighbouring 

 ■ clays. 



There are, of course, sand-beds in some of the sections in the 

 districts surrounding the typical sand area ; these may reach a 

 thickness of twenty odd feet. The sections described are fairly far 

 apart, but in places where sections are sufficiently close to one another 

 to allow of detailed correlation it may be shown that sand-beds of 

 more than 20 feet in thickness are purely local lenticles inter- 

 calated in the clays. Hence, in the absence of intervening sections, 

 it is impossible to state definitely that the sands of Moston, Alkring- 

 ton and Whitefield are continuations of the thick sands of Prestwich 

 and Kersall, and in the absence of such evidence there is no ground 

 for the belief that those sands constitute a definite stratum separat- 

 ing an Upper from a Lower Boulder-clay. 



Evidence of the rapid incoming and dying out of sand-beds is 

 given in several places. In the Fallowfield sewer cutting a lenticular 

 bed of sand makes its appearance below the clay, attains a thickness 

 of over 27 feet, and dies out again, all within a mile. A bore-hole in 

 Newton Heath shows a sand-bed of 29 feet which is not seen in a 

 second boring 150 yards to the east, nor in another 350 yards to the 

 south. There are many other sections which show the irregularity 

 of the deposits, but those mentioned are sufficient to demonstrate 

 that sands more than 20 feet thick may be purely local in character. 



Hull himself recognised the great variability of the Glacial 

 deposits, and accounted for the absence of the " middle sands " in 

 areas where he expected to find them by assuming that they had 

 been eroded. Evidence of the lenticular character of the deposits as 

 shown by the numerous sewer sections and the closely adjacent series 



