THE MICROSCOPE. 33 



caution of cleaning it with a cloth when one begins to work 

 is easily attended to. And the difficulty can also be over- 

 come by having the split tube that clasps the sliding body 

 of the microscope lined with leather or cloth. If a nose- 

 piece is not employed, this form of coarse adjustment is 

 the best, because the tube can be readily pulled out of its 

 split sheath when the lens is to be changed : for nothing 

 can be more inconvenient than attempting to screw or unscrew 

 a lens with the tube fixed over the stage; the hand being 

 placed in an unusual position, the lens is apt to fall, and 

 certainly much time is lost in getting the thread of the 

 screw to bite when the hand is thus placed. When a nose- 

 piece is employed, however, a coarse adjustment, consisting of 

 a rack and pinion finely made, is the best arrangement, for 

 then all jerking is avoided, and the spiral motion of the 

 tube, which is disadvantageous with a nose-piece, is unne- 

 cessary. 



FORMS OF MICROSCOPES. 



48. Monocular Compound Microscopes. Excel- 

 lent microscopes are made in this country by Ross, R. and 

 J. Beck, Powell and Lealand, Swift, Crouch, Collins, Baker, 

 Browning, and others : in Paris by Hartnack, and Verick : in 

 Jena by Zeiss. Their forms are well-nigh endless, and can- 

 not be considered here.* The main points required in 

 any compound microscope are (i), good lenses ; (2), per- 

 fect steadiness ; (3), power of easy adjustment ; (4), porta- 

 bility; (5), moderate cost. These qualities are wonder- 

 fully well united in the form of microscope (Fig. i) which 

 is very similar to that originally made at the request of the 

 late Professor Bennett, by Oberhauser, and now by his suc- 

 cessor Hartnack, and also by Ve'rick of Paris. English 

 opticians have been too much given to the manufacture of 

 machines of imposing appearance. Now, however, they 

 are wisely endeavouring to rival the cheap continental 

 microscopes, and it is by no means improbable that ere 

 long they will surpass continental makers in this direc- 



* The reader is referred to Dr. Carpenter's excellent work on 

 "The Microscope," 5th ed. 1875, for full information on this subject. 



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