CONSTRUCTION OF THE MICROSCOPE. 



securing small objects and holding them during 



tion, are all that is required for afield instrument 



a day's ramble. This useful little holder maybe purclwwaiE 



in a case at Mr. Weedon's, 41, Hart-street, Blcomsbroy. 



The Stanhope lens is similarly constructed, although outr 



so good and convenient as the former, and is but ^eidoK 



to be purchased properly made. 



When the magnifying power of a lens is considerable, 

 or when its focal length is short, and its .-proper disfcaafle 

 from the object equally short, it then becomes. neeesnqy 

 to be placed at a proper distance with great precision.; it 

 cannot therefore be held with sufficient accuracy nft 

 steadiness by the unassisted hand, but mast be mouaiaft 

 in a frame, having a rack or screw to. move it to wards ar 

 from another frame or stage which holds the object. & 

 is then called a microscope; and it is furnished, acoeci- 

 ing to circumstances, with lenses and mirrors to 

 and reflect the light upon the object, with other 

 nienoes. 



Fig. 23. Rott's Simple Microscope. 



The best of the kind was that contrived by Mr. 



represented in fig. 23 \ and consists of a circular font % 



from which rises a short tubular stem d, into wkiA 



D2 



