A NEW MICROSCOPE. 10g 

interfere with its complete rotation. The edge is graduated for 
goniometry, and finders are engraved upon the surface. A simple 
arrangement beneath the stage is provided for holding an iris 
diaphragm, hemispherical lens, or Wenham’s “half button.” ‘The 
sub-stage is provided with rectangular and rotary motions, and 
both stages can be removed, if necessary. The coarse adjustment 
is by means of a diagonal rack moved by a spiral pinion. The 
fine adjustment is effected by milled heads on both sides of the 
nose piece, operating on a vertical slide, which holds the objective. 
There are graduated arcs for measuring the inclination of the 
main limb and optical body of the swinging tail-piece, and the 
graduations on the base plate can be utilised in measuring the an- 
gular apertures of objectives. There are clamping screws in 
various positions for fixing the instrument, which is very firm and 
well balanced. y 
Some modifications of the leading principle introduced in the 
construction of this instrument have already been adopted by 
other makers, but in most of the previous inventions, the object 
under examination remained fixed in only one plane of motion of the 
optical tube. In 1866, M. Jaubert, of Paris, produced a micros- 
cope with a lateral inclining movement at right angles to the 
vertical motion of the body, by means of an axis running through 
the trunnion bar between two upright pillars; but the object under 
examination did not remain fixed in any plane of motion of the 
optical body. It was claimed by the maker that the tilting of the 
stage in this instrument would be found useful in chemical experi- 
ments. More recently, some American stands, such as_ the 
Centennial Zentmayer and the Acme of Sidle, have been provided 
with a rotating base, the object plane passing through the axis of 
motion of the optical body, so as to facilitate the measurement of 
the angular apertures of objectives without an apertometer. By 
this arrangement when the body was placed horizontally, the rotary 
motion of the base would tilt the object plane through 180° of 
azimuth without moving the object away from the light ; but in 
every other position of the body the object would move away. 
This principle has been adopted in this country in Ross’s Im- 
proved Zentmayer Stand, and in Beck’s International. Messrs. 
Watson and Sons have recently produced a stand in which the 
axes of motion, in both altitude and azimuth, pass through the 
object, so that the object plane may be tilted in every necessary 
direction with respect to the light, without moving the object from 
its position; but as the motion in azimuth is produced by a vertical 
pillar, which carries the main limb, moving round the circumference 
of a circular base, in some positions of the object plané, the 
object will be screened from the light altogether by the pillar being 
interposed. In other respects this stand approaches very nearly in 
