St James's School had been built where this great ice sheet finally stopped. When the ice retreated, melting away as a dirty sludge, it deposited its stones to form a great ridge from Muswell Hill, along East End Road and far beyond. The teacher showed us the geological map with the Boulder Clay marked in icy blue and Fortis Green at the southern edge, at the last position of this giant bulldozer. This was why there had been a road along Fortis Green for so long. The ridge of stones and rocks rose above the surrounding countryside, dry and easy walking, with clear views to north and south. It was a secure road, not to be moved until perhaps the next ice age. A triangle of Boulder Clay stretching for four miles from Muswell Hill to Hendon, was cut through later by the River Brent. The Boulder Clay extended past Whetstone to Chipping Barnet, with a tongue stretching out to Colney Hatch, just beyond the Great North Road.
The foundation stone of St James's Parish Hall, in Fortis Green Road, had been laid on the 26th of September, 1925, only about six months after I came to Muswell Hill. In my last year we began to have lessons in the upstairs room now occupied by the Nursery. Mr Broad, another teacher, used to assemble us in the St James's School yard in Fortis Green, and march us across to the new building. It was in those short walks that I first began to imagine the effect of the glacier on the surrounding area. One leg felt cold because of the immense glacier in Tetherdown towering above us, while the other leg, facing the southern sun, felt warm and comfortable. On the return journey the heat reversed itself. From then on I never walked along Fortis Green without imagining that I had one leg hot and the other cold.
The Old Gravel Pit in Coldfall Woods was best remembered later because it was just by the Tollington School cricket pitch. One day, bored with rolling the pitch, several of us dropped the roller into the pit, but this pit is recorded in the literature as follows:-
Ghosts of Victorian geologists haunted that pit, for this is where the detective work on the past history of Muswell Hill had started. Over the years geologists swarmed into the area, coming out from London on Saturday afternoons to poke about in the gravel for tell-tale rocks. Learned papers were written and hours of careful drawing and analysis were lavished on each specimen, yet here were idle boys dropping a cricket roller on their ghosts. Today the ghosts may rest peacefully because the Pit has been filled in and a level playiug field covers the site.