268 Progress in Science. [April, 
the liquid is in no way altered in its divergence when it passes through a flat 
transparent vessel. The surface of the liquid is perfe@tly transparent and 
does not catch the light. The cone of rays therefore continuing to expand as 
it approaches the defining lens /, passes 
Fic. 22. for the most part outside of it, and hence 
the imperfect illumination. The glass shade 
and its liquid contents form a converging 
lens, which throws the whole light incident 
on it through the lens /, and thus no light is 
lost. The course of the light is shown by 
the dotted lines. In Professor Morton’s 
apparatus, a horizontal lens is placed imme- 
diately under the flat-bottomed vessel con- 
taining the liquid to effe& the necessary 
convergence. In Dr. Ferguson’s arrange- 
ment the lens and containing vessel are 
one and the same thing. Such composite 
lenses were stated to be singularly accurate 
and effective, and give considerable latitude 
in regard to size. The glass dish used was 
8 inches in diameter, and was filled to form 
a lens 6 inches in diameter. It was cut from 
a shade whose cylindrical part was Io inches 
across. The surface of the liquid was in 
focus with the lens used at about 9 inches, 
but the waves were best seen when the 
lens was 15 inches distant. The dropping 
apparatus can be brought over any part of 
the surface, and the rapidity of the drop 
regulated by the stopcock. When the glass 
dish is full, different figures with upright 
sides of metal plate can be placed in it so as 
to alter the shape of vessel at will, and 
illustrate the conformation of the wave 
systems of plane figures of all kinds. The 
sides of these refle& the waves, and the 
outer edges can be darkened with paper 
so that only the inside is seen. The waves 
were exhibited by the aid of the lime-light, 
on a screen 15 feet in diameter, with sin- 
gular beauty and clearness. The same 
apparatus was used to illustrate a course 
of lectures on Sound, in the Edinburgh 
Museum of Science and Art. The screen employed in this case was a 
square sheet of ground glass, 3 feet in size, when the demonstrations could 
be distinctly seen by the audience in the full blaze of the gas of a hall well lit 
by sunlights. Spirits were used instead of water, as under the conditions they 
give a slower wave and a clearer definition. 
Lockwood and Co. will publish on April 1st the first number of a new Quar- 
terly, under the title of ‘‘ Naval Science,” a magazine intended to promote the 
improvement of Naval Archite@ture, Marine Engineering, Steam Navigation, 
and Seamanship. Its appearance is looked for with considerable interest 
in naval and scientific circles, as it is to be edited by E. J. Reed, C.B., late 
Chief Constructor of the Navy, and the contributors will include the most 
eminent authorities in the several branches of the above subjects. 
LIGHT. 
In the oxyhydrogen light the use of cylinders of burnt dolomite in place of 
ordinary lime is recommended as increasing the regularity of the light. 
