Acts 27:28

And sounded
Or let down their plummet, or sounding line; which was a line with a piece of lead at the end of it, which they let down into the water, and by that means found what depth it was, by which they could judge whether they were near land or not. The sounding line, with the ancients, was called by different names; sometimes bolis, and this is the name it has here, (bolisantev) , "they let down the bolis": and the bolis is, by some, described thus; it is a brazen or leaden vessel, with a chain, which mariners fill with grease, and let down into the sea, to try whether the places are rocky where a ship may stand, or sandy where the ship is in danger of being lost: it is also called "catapirates", which is thus described by Isidore; "catapirates" is a line with a piece of lead, by which the depth of the sea is tried. Herodotus makes mention of it under this name, and observes, that when persons are within a day's voyage of Egypt, if they let down the "catapirates", or sounding line, they will bring up clay, even when in eleven fathom deep ^F18 According to modern accounts, there are two kinds of lines, occasionally used in sounding the sea, the sounding line, and the deep sea line: the sounding line is the thickest and shortest, as not exceeding 20 fathoms in length, and is marked at two, three, and four fathoms with a piece of black leather between the strands, and at five with a piece of white leather: the sounding line may be used when the ship is under sail, which the deep sea line cannot. --The plummet is usually in form of a nine pin, and weighs 18 pounds; the end is frequently greased, to try whether the ground be sandy or rocky ^F19. The deep sea line is used in deep water, and both lead and line are larger than the other; at the end of it is a piece of lead, called deep sea lead, has a hole at the bottom, in which is put a piece of "tallow", to bring up the colour of the sand at the bottom, to learn the differences of the ground, and know what coasts they are on.

And found it twenty fathoms;
or "orgyas"; a fathom is a measure which contains six feet, and is the utmost extent of both arms, when stretched into a right line: the fathom, it seems, differs according to the different sorts of vessels; the fathom of a man of war is six feet, that of merchant ships five feet and a half, and that of fly boats and fishing vessels five feet: if the fathom here used was the first of these, the sounding was an hundred and twenty feet; the Ethiopic version renders it, "twenty statues of a man".

And when they had gone a little further, they sounded again, and
found it fifteen fathoms;
or ninety feet; by which they imagined that they were near the continent, or some island: in some places, as the coasts of Virginia, for instance, by the use of the deep sea line, it is known how far it is from land; for as many fathoms of water as are found, it is reckoned so many leagues from land.