Page:A Voyage of Discovery and Research in the Southern and Antarctic Regions Vol 2.djvu/357

] The mean time of high water at new moon is 4$h$ 45$m$; at the first quarter, 5$h$ 5$m$; at full moon, December. 6$h$ 28$m$; and at the third quarter, 5$h$ 9$m$ after she passes the meridian.

The highest tide is the third high water after the full or change of the moon.

The greatest rise and fall is 6 feet 2 inches at new moon; but at full moon it varied from 4 feet 10 inches to 6 feet, and averages a smaller spring tide than occurs at new moon.

The largest spring tide, or difference between high and low water, invariably occurred at a low water, and as invariably at the low water nearest to midnight.

The mean level of the sea was deduced from five months' observations; and two permanent marks were made 5 feet 8 inches above it, first by levelling the top of a rock a little to the southward of the pier and watering-place; and again by cutting a ledge in the face of the cliff close by it. Two copper plates were fixed in the rocks, marked thus: "5 feet 8 inches above the mean level of the ocean, August, 1842., H.B.M. ships Erebus and Terror;" by which any difference that may occur in the level of the sea in those parts may readily be detected.