eleven o'clock
The inspection gratified him ; the drain was like a great tunnel ; one might have driven a horse and wagon into it . Storri was especially struck by the fact that a considerable stream of water gushed from the drain 's mouth ; the stream had a fair current , four miles an hour at least , and showed a depth of full six inches . This was a discovery that set Storri 's wits in motion ; the drain boxed in a living brook . It was eleven o'clock that night when Storri returned to the mouth of the drain ; he was wrapped in a greatcoat and wore high boots . There were no houses about ; as for loiterers , the region was deserted after dark . Storri looked out on the broad bosom of the river ; he noticed that even at low tide a boat drawing no more than eighteen inches might push within a dozen feet of the drain . Satisfied that no one observed him , Storri stepped to the mouth of the drain and disappeared .