When making preparations in New Haven for the "bathymetric survey of Lake Parinacochas," suggested by Sir Clements Markham, we found it impossible to discover any indication in geographical literature as to whether the depth of the lake might be ten feet or ten thousand feet. We decided to take a chance on its not being more than ten hundred feet. With the kind assistance of Mr. George Bassett, I secured a thousand feet of stout fish line, known to anglers as "24 thread," wound on a large wooden reel for convenience in handling. While we were at Chuquibamba Mr. Watkins had spent many weary hours inserting one hundred and sixty-six white and red cloth markers at six-foot intervals in the strands of this heavy line, so that we might be able more rapidly to determine the result in fathoms. Arrived at a low peninsula on the north shore of the lake, Tucker and I pitched our camp, sent our mules back to Puyusca for fodder, and set up the Acme folding boat, which we had brought so many miles on muleback, for the sounding operations. The "Acme" proved easy to assemble, although this was our first experience with it. Its lightness enabled it to be floated at the edge of the lake even in very shallow water, and its rigidity was much appreciated in the late afternoon when the high winds raised a vicious little "sea." Rowing out on waters which we were told by the natives had never before been navigated by craft of any kind, I began to take soundings. Lake Titicaca is over nine hundred feet deep. It would be aggravating if Lake Parinacochas should prove to be over a thousand, for I had brought no extra line. Even nine hundred feet would make sounding slow work, and the lake covered an area of over seventy square miles.