4i22 Capt. Kater's improved Method of dividing 
adjustable dots has been described. The silver tongue with 
its cross lines is represented at A, plate XV. fig. i. 
The three microscopes are similar to those used in reading 
ofl^the divisions of astronomical instruments of modern con- 
struction, and therefore need not be very particularly described. 
Two of these microscopes are furnished with micrometers in 
the usual manner, each having a set of cross wires as repre- 
sented at fig. 6, moveable in the direction ah^ by means of the 
micrometer screw. 
The two micrometer microscopes have adjustable supports, 
one of which is seen at fig. 4. in which are two pieces of 
brass forming a dovetail groove for the sliding piece A, which 
carries the microscope, and which is moveable by the screw 
represented in the plate. In the circular opening formed in 
the sliding piece A, a piece of brass tube is soldered, in which 
the microscope slides rather stiffly, in order to be adjusted to 
distinct vision. The supports are made very strong, and are 
furnished beneath with clamps, by which, or by any other 
equivalent contrivance, they may be firmly fixed to an arp, 
hereafter to be described. One of the microscopes with its 
support is represented at fig. 5, from which its construction 
will be readily understood ; the micrometer head is omitted in 
the engraving, as it would only occasion confusion. The 
object glass of each microscope is fixed in a tube having a 
fine screw cut on its outside, by means of which, after the 
microscope has been adjusted as nearly as possible to distinct 
vision, any remaining parallax may be removed, when the 
object glass is to be secured by the nut a, in the usual manner. 
Fig. 7, represents the support for the third microscope, and 
also the cutting point, the frame of which is attached to this 
