irradiation from the white paper, and recommends a thickening of the cross-strokes at the ends to obviate this defect. This observation is less applicable to the German letters, for they already have broken lines and knobbed expansions at the ends of the strokes. Many physicians, particularly those who are not Germans, believe that the shape of the German letters is more tiresome to the eyes than that of the Roman letters, I have never been able to perceive this, nor any reason why it should be so, provided the German print is large and thick enough, and the lines are far enough apart. Use has doubtless much to do with the matter. For myself, it is always pleasant, after a long reading of the monotonous Roman print, to return to "our beloved German."
Even the thickest and largest letters, the shortest and best separated lines, and the most excellent printing, may speed the progress of myopy if the light is bad. At home, every one can find a light place to read—by the window on dark days, by a bright lamp at night. It is different in schools and offices. Fifteen years ago, after measuring the ratio of the window-space to the floor-space in the schoolhouses of Breslau, I declared that there could never be too much light in a schoolroom, and estimated that unless the house could be furnished with a glass roof, at least thirty square inches of window-space should be provided for each square foot of floor-space. In many schoolrooms as at present arranged, the pupils nearest the windows may be sitting in a glare of light, while those farthest away are not able to study for the obscurity. Notwithstanding all that has been written and all that has been done in the last fifteen years for the improvement of school-rooms, enough is still left to be done in nearly every town.—Deutsche Rundschau.
By J. G. BUCHANAN, F.R.S.E.,
OF THE CHALLENGER EXPEDITION.
THE first problem of deep-sea investigation is to determine the extent of the ocean, its size, its volume. The superficial extent and limits are determined by the surveyor. In order to map out the bottom of the sea, there is only one method, namely, the direct determination of the depth at as many places as possible. When a ship is "in soundings," the depth is ascertained by the ordinary hand lead-line, which is from twenty to twenty-five fathoms long, and is conventionally marked at stated intervals with bits of leather, white,
- Abridged and condensed from an address delivered before the Society of Arts, February 24, 1881.