Perrault was in a hurry, and he prided himself on his knowledge of ice, which knowledge was indispensable, for the fall ice was very thin, and where there was swift water, there was no ice at all.
佩罗着急赶路, 对自己了解冰雪知识很是自豪。这种了解是必不可少的, 因为秋天的冰很薄, 而且在水流湍急的地方, 根本就没有冰。