COLLINS'S BINOCULAR. 95 



in any direction with great facility. This can be readily 

 detached when it is desired to clear the stage for a frog- 

 plate, &c. The instrument is furnished with a dividing 

 set of powers, working with a tolerably flat-field ; dia- 

 phragm, condenser for opaque objects, live box, &c. The 

 whole packs in a neat case, measuring only 8x6 inches ; 

 forming one of the most portable microscopes for the use 

 of the student we have seen. 



The Binocular manufactured by Mr. Collins (Great Titch- 

 field Street, Portland Place), is constructed on the model 

 suggested by Dr. Harley, and contains all the recent im- 

 provements for combining rapidity of application with 

 simplicity in manipulation. Indeed, so far as the saving 

 of time is concerned, we scarcely know how a change for 

 the better could be devised. The whole of the appliances 

 of the instrument, prism, polariscope, stage condenser, 

 objectives of both high and low powers, &c. are attached 

 to the microscope itself, and that, too, in such a manner 

 as to enable the observer to place them in exact position 

 without the turn of a single screw or a moment's delay. 



CoUins's Binocular, represented in fig. 50, is fitted into 

 the bottom of a mahogany box, which forms at the same 

 time the stand ; round it a groove is run to receive the 

 lip of a glass shade. The instrument itself is made of 

 polished brass, and is eighteen inches high. The eye- 

 pieces are supplied with shades {a a) to protect the eyes. 



At the end of the transverse arm (/) is the box which 

 contains both Wenham's binocular prism and the analyser 

 of the polariscope ; and by merely drawing it a little out, 

 or pushing it further in, the instrument can be instantly 

 changed from a binocular to a monocular, and still further 

 to a polarising microscope. 



Immediately beneath (/) are the two objectives, a 

 quarter and an inch ; so that, in order to change the 

 power, all that is necessary is to slide them backwards or 

 forwards. Moreover, these are fitted with the universal 

 screw, so that either of them may be detached, as in an 

 ordinary instrument, and a quarter, or one-eighth, or other 

 power put in its place, at the option of the observer. The 

 instrument is fitted with a coarse and fine adjustment, and 

 has the additional advantage of a magnetic stage, in the 



