It struck me after a while that my friend Tardif was unusually silent. The shifting of the sails appeared to give him plenty to do; and to my surprise, instead of keeping to the ordinary course, he ran recklessly as it seemed across the _grunes_, which lie all about the bed of the channel between Guernsey and Sark. These _grunes_ are reefs, rising a little above low water, but, as the tide was about half-flood, they were a few feet below it; yet at times there was scarcely enough depth to float us over them, while the brown seaweed torn from their edges lay in our wake, something like the swaths of grass in a meadow after the scythe has swept through it. Now and then came a bump and a scrape of the keel against their sharp ridges. The sweat stood in beads upon Tardif's face, and his thick hair fell forward over his forehead, where the great veins in the temples were purple and swollen. I spoke to him after a heavier bump over the _grunes_ than any we had yet come to. "Tardif," I said, "we are shaving the weeds a little too close, aren't we?" "Look behind you, Dr. Martin," he answered, shifting the sails a little. I did not look behind us. We were more than half-way over the channel, and Guernsey lay four miles or so west of us; but instead of the clear outline of the island standing out against the sky, I could see nothing but a bank of white fog. The afternoon sun was shining brightly over it, but before long it would dip into its dense folds. The fogs about our islands are peculiar. You may see them form apparently thick blocks of blanched vapor, with a distinct line between the atmosphere where the haze is and where it is not. To be overtaken by a fog like this, which would almost hide Tardif at one end of the boat from me at the other, would be no laughing matter in a sea lined with sunken reefs. The wind had almost gone, but a little breeze still caught us from the north of the fog-bank. Without a word I took the oars again, while Tardif devoted himself to the sails and the helm. "A mile nearer home," he said, "and I could row my boat as easily in the dark as you could ride your horse along a lane." My face was westward now, and I kept my eye upon the fog-bank creeping stealthily after us. I thought of my mother and Julia, and the fright they would be in. Moreover a fog like this was pretty often succeeded by a squall, especially at this season; and when a westerly gale blew up from the Atlantic in the month of March, no one could foretell when it would cease. I had been weather-bound in Sark, when I was a boy, for three weeks at one time, when our provisions ran short, and it was almost impossible to buy a loaf of bread. I could not help laughing at the recollection, but I kept an anxious lookout toward the west. Three weeks' imprisonment in Sark now would be a bore.