1897 - 98 .] J. Boeke on derivation of Curves of Vowel Sounds. 91 
The microscope, C, used to examine the impressions on the 
phonograph cylinder, may slide up and down along its standard, 
and may be fastened at the proper height by a screw, D. The 
foot of the microscope is movable in a wooden sledge, E, along 
which it may be moved forward and backward till the proper 
situation for accurate examination of the impressions is found. 
Generally it should be moved a little beyond the axis of the 
cylinder, in order that sufficient light should fall upon them. 
The sledge, E> together with the microscope which it carries is 
movable parallel to the axis of the cylinder, H, by means of a 
cogged bar, FF, and pinion, 0, and its position may be accurately 
determined by a scale, SS. By this arrangement it is possible to 
find again any mark on the surface of the cylinder, H, the position 
of which has once been determined by means of the microscope. 
But as it happened sometimes that the cylinder moved a little 
on the mandrill, it was necessary to make quite sure of the identity 
of the observed marks ; this was done by means of a cross mark, 
