ge of them all! Take an instance. Let a leadsman cry,
'Half twain! half twain! half twain! half twain! half twain!' until it
become as monotonous as the ticking of a clock; let conversation be
going on 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 lot 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 you could if your
memory had been patiently and laboriously trained to do that sort of
thing mechanically.

Give a man a tolerably fair memory to start with, and piloting will
develop it into a very colossus of capability. But ONLY IN THE MATTERS
IT IS DAILY DRILLED IN. A time would come when the man's faculties could
not help noticing landmarks and soundings, and his memory could not help
holding on to them with the grip of a vise; but if you asked that same
man at noon what he had had for breakfast, it would be ten chances to
one that he could not tell you. Astonishing things can be done with the
human memory if you will devote it faithfully to one particular line of
business.

At the time that wages soared so high on the Missouri River, my chief,
Mr. Bixby, went up there and learned more than a thousand miles of that
stream with an ease and rapidity that were astonishing. When he had seen
each division once in the daytime and once