is no extravagant mass of knowledge, and no marvellous facility, compared to a pilot's massed knowledge of the Mississippi and his marvellous facility in the handling of it. I make this comparison deliberately, and believe I am not expanding the truth when I do it. Many will think my figure too strong, but pilots will not.
And how easily and comfortably the pilot's memory does its work; how placidly effortless is its way; how unconsciously it lays up its vast stores, hour by hour, day by day, and never loses or mislay's a single valuable package of them all! Take an instance. Let a leadsman cry, "Half twain! half twain! half twain! half twain! half twain!" until it becomes as monotonous as the ticking of a clock; let conversation be going ow all the time, and the pilot be doing his share of the talking, and no longer consciously listening to the leadsman; and in the midst of this endless string of half twains let a single "quarter twain!" be interjected, without emphasis, and then the half twain cry go on again, just as before: two or three weeks later that pilot can describe with precision the boat's position in the river when that quarter twain was uttered, and give you such a let of head-marks, stern-marks, and side-marks to guide you, that you ought to be able to take the boat there and put her in that same spot again yourself! The cry of "quarter twain" did not really take his mind from his talk, but his trained faculties instantly photographed the bearings, noted the change of depth, and laid up the important details for future reference, without requiring any assistance from him in the matter. If you were walking and talking with a friend, and another friend at your side kept up a monotonous repetition of the vowel sound A, for a couple of blocks, and then in the midst interjected an R, thus, A, A, A, A, A, R, A, A, A, etc, and gave the R no emphasis, you would not be able to state, two or three weeks afterward, that the R had been put in, nor be able to tell what objects you were passing at the moment it was done. But yon could if your memory had been pa-
