24 _ W. Grunow—A New form of Cathetometer. 
sliding on the rod and placed over each other, one of them 
being provided with a clamp, and connected with its mate by a 
micrometer screw and spring, or by the former alone. 
This form of fine adjustment seems to thave been derived 
from that employed in the earlier compound microscopes, and 
though its manifest defects have long since caused its disuse 
with these instruments, it is still ordinarily employed in the 
construction of cathetometers 
have recently ae for the Physical Cabinet of 
Columbia College, a cathetometer, in which, by the use of an- 
other arrangement, great steadi- 
ness and accuracy of movement 
are attained, in combination with 
simplicity. 
on a_ graduated, vertical, 
telescope and the micrometric 
a for the fine adjust- 
ent. On one of the sides of this 
and accurately. The slide B is 
moved up and down the block 
the micrometer screw C, 
which is mounted in such a way 
that its motion cannot interfere 
with the steadiness of the move- 
ment of the slide B; it can ais be adjusted so that it works 
without dead motion. 
Each turn of the screw corresponds with one division of the 
graduated bar on which the block A slides. The slide B carries 
an arm with an index v, which moves in an opening O, cut out 
in the side of the block A corresponding to the stadustion on 
the bar. e screw carries a movable head, divided into one 
* Compare Lega. de oe par M. P. Desains, vol. i, p. 12; Die Physik 
auf Grundlage der Erfahrumg, von Dr. Alb. Mousson. 2d ed., ay i, p. 15; Lehrb 
der Physik umd oo ar Joh. Miiller, 6th ed., vol. ii, p. 569; Lehrbuch 
: A. Wiilner, vol. i i, p. 43; hee de Physique, par 
M. J. segs § od a vol. i = 36; Elementary Treatise on Natural Philosophy, 
A. 2; Allgemeine Encyklopaedie der 
