ON THE CHOICE OF A MICROSCOPE. 159 
Now, with regard to the comparative advantages in the 
first-class microscope stands by our chief makers, it must of 
course be borne in mind that one advantage cannot be gained 
to the utmost degree without the sacrifice of some other 
convenience. Thus to take the example of the traversing 
stage movement, 3-inch motion in rectangular directions, is 
not nearly sufficient for the purpose intended, though many 
first-class instruments are made only with that. You will 
find yourself continually baulked by unexpectedly coming to 
the end of your tether. So much does Mr. Pillischer value 
great range of motion in this part of the instrument, that 
his No. 1 stand is constructed with nearly 14 inches of 
motion in each direction; but if you wish for that luxury 
you must make up your mind to the inconvenience of a bulky 
microscope, and to the loss of the circular rack. Again, 
so much does Mr. Powell prize the advantage of the circular 
rack movement, that his great instrument is so constructed 
as to enable it to make an entire revolution of a circle when 
required, not only % of a revolution, as is the case in Mr. 
Ross’s instrument; but then if you covet that convenience, 
you must make up your mind to put up with a limited range 
of stage motion, and a somewhat unwieldy stand. Mr. 
Ross, however, striking the balance between these two 
advantages and disadvantages, secures a l-inch motion in 
rectangular directions to the traversing stage; a 3 revolution 
of a circle to the circular rack, which are sufficient for all 
practical purposes; while the entire instrument is not too 
heavy to be carried in one hand, though immoveably- firm 
when once placed on its pedestal. Messrs. Smith, Beck, and 
Beck’s large microscope possesses many excellent qualities. 
Its double body and stage are supported by a solid brass limb, 
with the rack movement attached to the body itself, giving 
great strength and security to that part of the instrument, 
but the power is lost thereby of turning the body, when 
required, out of its axis altogether away from the stage—a 
convenience belonging to the first-class microscopes of our 
other great makers. At the sacrifice of this and some other 
advantages, Mr. Smith’s instrument, though of exquisite 
workmanship, is less costly, and lighter in its general 
build than theirs—merits that are sure to be appreciated by a 
large class of purchasers. Where, however, expense need not 
nosepiece, polariscope, and mahogany box, is £60. The addition to the l-inch 
and 3-inch object-glasses, of a 2-inch glass, and which would make the instru- 
ment quite complete would raise the cost to 60 guineas. A similar micro- 
scope of Mr. Powell’s would be about the same price, those of Messrs. Smith 
and Pillischer, some few pounds less. 
