a" 
British Association for the Advancement of Science. 291 
first elevated above the surface, and then permitted to subside. 
Now they found. that whenever the displacement took place, as 
in the wave, they had the phenomena of least resistance. “So 
that in forming a floating vessel with this wave-line disposed on 
alternate sides of the keel, so as to give such motion to the parti- 
cles as to displace nothing more than was necessary, nor.for a 
greater distance than was necessary to allow the vessel to. pass, 
they obtained the solid of least resistance. Since that time, a 
variety of experiments on large vessels had been performed ; 
essels were now constructing on this form; and it was a 
remarkable fact, that the fastest vessel on the Thaines was one 
to which this juli had been given. It was scarcely credible, 
that a vessel should move at the rate of fifteen miles an hour, 
and not raise a spray,—not raise anything like that high mass of 
water which was always found at the bows of vessels going at 
speed, but enter the water perfectly smooth, and leave it smooth, 
and as much at rest in the direction of the displacement as it was 
before: the floating solid ‘passed... This phenomenon had i invari- 
ably accompanied all the vessels formed on this line. .- 
On some Preparations of the Eye, by-Dr. W. Clay Wallace. 
Sir D. Brewster exhibited a series of beautiful preparations of the 
eye, made by Dr. W. Clay Wallace, an able oculist in New York, 
calculated to establish some important points in the theory of 
vision. As no paper accompanied these preparations, Sir D. Brew- 
ster explained to the meeting their general nature and importance. 
Dr. Wallace, he stated, considers that he has discovered the appa- 
Yatus by which the eye is adjusted to different distances. "This 
adjustment is, he- conceives, effected in.two ways,—in eyes, 
which have spherical lenses, it is produced by a falciform, or — 
hook-shaped muscle attached only to one side of the lens, which 
by its constriction brings the crystalline lens nearer the retina. 
In this case, it is obvious that the lens will have a slight motion 
of yotation, and that the diameter, which was in the axis of vision 
previous to the contraction of the muscle, will be moved out of 
that axis after the adjustment, so that at different distances of the 
lens from the retina, different diameters of it will be placed in © 
the axis of vision. As the diameters of a sphere are all equal 
and similar, Dr. Wallace considered that vision would be equally 
perfect-along the different diameters of thelens, brought by ro- 
lation into the axis of vision. Sir D. however, remarked, that 
