On March 5, at time of high tide, the Staff sailed to the farthest point northeast from which the target could be seen with the telescope. To the naked eye, the target was entirely invisible. The horizon seemed to occult the lower limbs of the belt of mangrove trees constituting the background of the view.

Over the water at the point of observation, the telescope was fixed at an altitude of 30 inches above the water, and through it the target stood out in bold relief. The instrument was then lowered to within 18 inches, with the same observed results. Afterward, at the height of 10 inches above the water, the entire surface of the target was still visible.

Very careful observations were made and repeated with the telescope at this altitude. The target was clear cut and well defined, and even the space between the bottom of the target and the water was observable. Then, to make the test absolutely satisfactory and conclusive, the telescope was fixed upon the water's surface; with the instrument almost touching the water--indeed, it could not be placed closer without wetting the lenses--long and careful observations were made. There could be no mistake; the entire surface of the target could be seen, with a small dark line of the background appearing beneath it.

The terrestrial eyepiece was then exchanged for

With the telescope at the same altitude, the cross-bar was observed to be a little below the top of the tar-get, with the target foreshortened by perspective to a breadth equal to about one half the length of the stake. With the visual axis of the telescope 2 inches above the water, the cross-bar was seen to be in line with the top of the target.

Besides this observation, an absolutely satisfactory view was had of the water surface itself. With the telescope placed absolutely level, the water appeared to slope gradually upward to the center of