Four days later, a firing room was built in the backyard at North Slope Mine.
Two deep holes were dug in the yard, each one was round, with a narrow top and a wide bottom. The front diameter was about 20 centimeters, while the rear end was enlarged to 26 centimeters. Roland intended to use these holes to cast the mold. The hole had already been baked by Anna, and the surface of the soil was sintered into a whole like an outer shell. The chamber faced downwards so that a better wall quality could be achieved during casting. If the chamber were placed higher, more dross and bubbles would be produced. All the cave sizes were calculated by shells as he vaguely remembered that the so-called six-pound and eight-pound cannon were named according to the weight of their shells. So a few 12-pound iron balls were poured out, and the ball diameter plus barrel wall thickness were used to calculate the mold diameter.
