Beck^ 0)1 the Universal Achromatic Microscope. 15 
this arrangement the field of view is not cut off when the 
objects are viewed as transparent with the highest power. 
If the single body only be required^ the prism can be pushed 
back by the small, milled head (g) ; or when this is unscrewed, 
it can be taken out altogether, for the purpose of being wiped. 
We may here mention that the manufacture of this instru- 
ment is so arranged as that the change from the square body 
(PI. V) to the binocular or other body (PL VI) can 
be made by any one, and with great facility ; so that to add 
these, or any other parts which are alluded to in this paper, 
it will not be necessary for the microscope to go into the 
hands of the manufacturers, or of any skilled workman. 
As to the necessity for the next addition, there may be 
different opinions. We have not previously stated that the 
spring (PI. V) which holds down the stage-plate (k) can be 
removed by unscrewing; after this is done the stage is 
perfectly clear, and any large object, or a small saucer or 
dish, can be placed upon it. It will also then receive what 
is commonly called a stage with actions (PI. VI, fig. 3) ; 
this is contrived so to fit on as to admit of its being turned 
round as a whole, and consequently always central with the 
body; or, in other words, during the rotation the object will 
not move out of the field of view ; the amount of movement 
at right angles is half an inch each way, and is effected by 
means of the milled heads (i, k) ; the object can be moved to 
and fro on the ledge (l) which also slides up and down, and 
a small spring can be turned to clamp the object when 
necessary. 
The following extra pieces of apparatus can also be 
added ; but as they require no description here, we merely 
enumerate them to give some idea of the capability of this 
form of stand : 
Polarizing apparatus, consisting of two Nicol's prisms and 
plate of selenite. 
Wenham^s parabolic reflector, for dark field illumina- 
tion. 
A dark well; and Lieberkulm^s to the I-inch and ^-inch 
object-glasses, for additional opaque illumination. 
Wollaston^s camera lucida, by which, with the aid of a 
stage micrometer, any drawing or measurement can be 
made. 
A small live box, and a glass trough. 
At the conclusion of this description (for the length of 
which we must apologise), whilst not contending for one 
moment that the performance of this microscope will equal 
that of our first-class instruments^ we are sure it will most 
satisfactorily exhibit nine tenths of the microscopic researches 
