THE FLSE AD.TUST3EEN: 1 7 



: 



at C. r.ti>e- or lower.- the body with gi-eat smoothness and with - 

 great delicacy of ^.vrrth inch : :y revolution of the milled head. 



and therefore capable of yielding _ rvice with the highest p 

 objectives. 



"SVe mav now dii-ect oui- attention to the - - . 



* 



into which we have separated riie various kinds of fi: - 



viz. that in which the - - -""-. Ijusti 



screw. 



v -is one of the new forms of fin- 



ment worthy >f careful trial : it has in it elemei." s of great 

 It can. how- . iily be ap^ the L>:~r model, and with 



adjustment described alx>ve certainly places this f.-iTLi ::" mi< : - 

 l^eyond the danger that soon - _ promi- .ave pi- 



extinction as a first-class microscope. 1 



Th' f (188 - -ound in principle and 



ingenious in c:>n-triKti-'U. ui^-i although the patent 

 modification - of it 1 88s . we believe th- rm, wl 



makes, to l>e the best. because it only ts - '-iece whil^ - 



modification acts on the body-tube. 



The earlv form emploved bv Swift 



* .L 



necessity of all > ssful fine adjustments : - - - the 



accuracy and perfection of the fitl _ - - 



was done, as >hown in fig. 1- tl _ - 



bar. A. to tlu - -d slid: - in V _ 



at the back of the K.-ly. A I ber s 



milled head. F. ts n a vertical Ivut lev- n whicl ~- . K. 



fixed to the pi-ism bar bears. 



Thei-e is al>o an adjustment _ :iing up the prism bar in 



the V-grooves. B B. Siti 



with this form of adjustment : while the power to tighten up " by 

 means of tl -tan-headed screws enables; wear and tear to be 



c.nnptMi-ated. It is obvious that the slowness of the motion is here 

 c >nnvl'. "iiree factors : (1) the length of the lever. D: (2) the 



listaj ' the lifting-stud. E. from the pivot or fiilcnun : and 

 the pitch of the screw -thread on F. 



V -.ufestlv. where a siW-e-lever fine adjustment such as this is 

 employed it should be. as it now always is, placed on the f<?tf-hand 

 side of the operator : we can readily focus with the left hand, and 

 leave the right hand free tor moving the slip and effecting other 

 adjustments. Ambi-dexterity is not at present a common gift, and 

 to have the right hand five is important. This was pointed out by 



Mr. Nelson when tliis fine adjustment was first introduced, and he 

 had a student's microscope constructed with the micrometer milled 

 head on the left side, as in fig. 134. It is manifest, however, that 

 it would greatly improve this adjustment if the screw-pinion 

 weiv carried right through and a milled head placed on both the 

 right and the left sides of the body. 



\ rlv form of a wvy-oiVtv-aJH/rt - : was em- 



% M. r tf 



ployed by Andrew Ross. It was applied to a microscope having a 



>*rw. if.Af.S. (18S1) 

 rm. If.-V.S. (1SSS' p, 120 and ilSsS*) p. 104S, fig. 207 



