368 



Mr. Highley's Condenser. 



MR. HIGHLEY'S CONDENSER. 



Me. Highley has devised a modification of Webster's condenser, 

 which possesses some very striking and important advantages. 



The drawing which 

 we append shows the 

 form of the instru- 

 ment. Its optical 

 part consists of "a 

 double concave lens 

 cemented to a very- 

 deep crossed lens/' 

 and the mechanical 

 arrangements are 

 efficient and com- 

 plete. The advan- 

 tage of this new 



Mb. Hisbxey's Condenses.— Upper side, showing the revolv- CO 13 denser Over the old 

 ing diaphragm A, and the milled head B, which opens or ■ ri of+Q T ma io -n/~>+ +1-.Q + it- 

 closes the shutter shown in the under view, patterns is not tna^iu 



is superior to them 

 under all conditions ; indeed, for some purposes, Powell and 

 Lealand's form, with its enormous angle of aperture, would be 

 preferred ; but the Highley condenser meets a greater num- 

 ber of everyday requirements 

 than any other condenser yet 

 produced. It works well with 

 powers from one inch upwards 

 to the highest. When very low 

 object-glasses, such as three 

 inch, are used, it must be re- 

 moved whether light or dark 

 ground illumination is desired ; 

 but the greater majority of mi- 

 croscopic observations are made 

 with powers of from one inch 

 upwards, and for these the new 

 condenser is very efficient. With me. highley's condenser.— Under side. 



flr> inrh nv twn rVn'WU fnr p-srim The lozenge-shaped opening represents 



an men or wo-inii as, 101 exam- the shutter partlally closed> and shutting 



pie, it affords an excellent light oir peripheral rays. 



ground illumination, instantaneously changed to a good dark 

 ground one by moving the circular diaphragm carrying the 

 stops. If a quarter or even a one-twentieth has to be em- 

 ployed, the condenser need not be changed, as it works well 

 with high powers, bringing out delicate diatom markings, and 

 the wedge-shaped patterns on the Podura scale, with the light 

 marks so admirably shown in Mr. Richard Beck's engravings. 



