ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



1043 



Fig. 207. 



The author then discusses the objection that the inclination of the 

 stage is a " barbarous " device, and says that he has used it success- 

 fully with objectives as high as a 1/10 in., but to obviate all annoy- 

 ance from this objection, he has adopted Dr. Elsberg's idea of multiple 

 cams, one at each corner of the stage ; the two distal cams being on 

 the same axis, and the two proximal cams on the same axis. A rod or 

 rods connect the arm levers, and springs hold down the stage on the 

 bed stage plate. The combined action of these cams gives hori- 

 zontal motion. 



Swift's Paragon Microscope (Wale's form).— In this Micro- 

 scope (fig. 208) Messrs. Swift have adopted the form of inclining limb 

 devised by Mr. George Wale, of the United 

 States, which we have repeatedly described. 

 The increased curve of the limb allows complete 

 rotation of the mechanical stage. The center- 

 ing and rotating substage is furnished with rack 

 movement, on which it is applied by a dove- 

 tailed slide. The mirror, with gimbal, two 

 arms, and rotating socket, slides on the tail- 

 piece, which is hinged to swing laterally on the 

 end of the limb. 



To this instrument Messrs. Swift have 

 applied a new arrangement of fine-adjustinent 

 which they have patented. The mechanism is 

 shown in fig. 207, where A A is the body-tube 

 (the middle part cut away to show the action). 

 This is connected at either end at the back 

 with a chamfered slide, fitted to move accurately 

 and lightly on the front of the coarse-adjustment 

 slide B B of the usual " Jackson " form, a spiral 

 spring above and at the back pressing it down- 

 wards. A long lever D is attached to the 

 plate B B, to pivot at E ; by the action of the 

 milled head F, on the lower end G of the lever, 

 the lifting stud C, connected with the cham- 

 fered slide behind the body-tube B B, is raised 

 very slowly through a focusing range of about 

 1/10 in. ; the reverse action of the screw allow s 

 the spiral spring above to press the slide down- 

 wards. 



By this very simple mechanism the fine- 

 adjustment is applied to the front of the coarse- 

 adjustment, and acts on the whole body-tube, 

 and not merely on the nose-piece, so that the 

 magnification is not altered by changes in the 

 focal adjustment. It is obvious that the slow- 

 ness of the motion is here controlled by three 



factors: (1) the length of the lever D, (2) the distance of the lifting- 

 stud C from the pivot or fulcrum E, and (3) the pitch of the screw- 

 thread on F. We understand that Messrs. Swift anticipate being able 

 to adapt this system of focusing to all their better class of instruments. 



3 y 2 



