British Association for the Advaiicement 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 ; 

 steam- vessels were now constructing on this form ; and it was a 

 remarkable fact^ that the fastest vessel on the Thames was one 

 to which this form 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 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- 

 ratus by which the eye is adjusted to difl'erent 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 construction brings the crystalline lens nearer the retina. 

 In this case, it is obvious that the lens will have a slight motion 

 of rotation, 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 diff"erent distances of the 

 lens from the retina, difl"erent 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 the lens, brought by ro- 

 tation into the axis of vision. Sir D. however, remarked, that 



