3 78 



LOBB, ON A NEW MICROSCOPK. 



mentj and working on this gun-metal plate acts as a 



goniometer^ and useful also in 

 many other respects. The stage 

 itself has all the usual move- 

 ments^ and is strongly screwed 

 to that portion of a circle which 

 works in^ and entirely round 

 the large brass circle^ and this 

 movement is so delicate that 

 an object can be kept in the 

 field of view during an entire 

 revolution with the -tir object- 

 glass^ &c. 



I have had Wenham's bin- 

 ocular arrangement added to my 

 microscope^, by Messrs. Powell 

 and Lealand, whose method of 

 doing it is highly satisfactory. 

 They remove, for this purpose, 

 the single body entirely, and put 

 on a double body firmly screwed 

 together, (it does not of course 

 prevent the single body being 

 used when required,) this en- 

 ables them to make a great im- 

 provement, which is the rack 

 and pinion movement to the 

 draw-tubes for adapting cor- 

 rectly the width of the eye- 

 pieces to the eyes, it being 

 essential to the due performance 

 of the binocular microscope, 

 that the centres of the eyes and 

 eye-pieces should coincide, and 

 the correction for this purpose is easily made by the rack and 

 pinion movement ; they have also retained their large field of 

 view, which for some objects is most desirable. 



