by means of a Revolving Lantern. 3138 
Although the performance of this instrument was highly 
satisfactory, it was exceeded in the following modification, 
(fig. 2), which, though hitherto unpublished, has been publicly 
used by me during the last three years. 
The advantages of a sensitive flame, which is made to re- 
volve in the vertical plane, must be obvious. Not only are all 
the teeth representing the soun 2. 
waves brought within the field of 
vision, and the foreshortening of 
the teeth upon either side avoided, 
but by the introduction of oxygen 
into the lantern the brilliancy of 
the flame is greatly increased. It 
is important that the lantern and 
other moving parts be made as 
light as possible. The thin mica 
cover of the lantern is conveniently 
d 
removed. The thin metal is folded 4.0 
over the edges of the mica which >= 
are to be brought into contact, and 
they are then held in place by a 
harrow strip bent traversely upon 
itself until it has the section of the 
