NEW HUYGHENIAN EYE-PIECE 



377 



objective can stand, and as a rule even the centre of the field will 

 not bear comparison in sharpness with the Huygheniaii form. 



Mi 1 . Kelson has recently computed and had made a Huyglieiiian 

 eye-piece on a wholly new formula l which has the field reduced by 

 about 7 inches, yet we can testify that in use it gives exceedingly 

 sharp images, and what surprises the accustomed worker is that it 

 acts admirably in the place of 'compensated' eye-pieces, giving 

 results that often not only equal but surpass these. 



The power of this eye-piece is 12 ; equivalent focus, - 8, corrected 

 for the English tube (;>=9'5). 



Fig. 324 is enlarged twice. 



\ 



Fi. 3'24. Nelson's new formula Huyglieniau eye-piece. 



Data: Glass, borosilicate crown, ^ = 1'51. r=64'0, Jena cata- 

 logue No. 5. 



Field-lens, biconvex r= + '94) ,. 



- diameter 00. 

 s= 2'94j 



Eve-lens, biconvex r'= + - 34) v .,,. 



J , ,- diameter '30. 



s = I'Ul ) 



Distance of eye-lens from field-lens, measured from their sur- 

 faces, "97. 



Distance of diaphragm from surface of field lens, "48. 



Diameter of hole in diaphragm, '2(3. 



Power, 12 ; equivalent focus, -53, corrected for the Continental 

 tube (p=6-3). 



Data : Glass, same as before. 



Field-lens, biconvex ^ + ^51 diameter via. 



Eye-lens, biconvex /= =+ -221 diameter - 20 . 



s= 'bo] 



Distance of eye-lens from field-lens, measured from their sur- 

 faces, '66. 



Distance of diaphragm from surface of field-lens, '34. 

 Diameter of hole in diaphragm, '16. 



These eye-pieces should enter the tube of the microscope as far 

 as their diaphragms. 



Positive Eye-pieces. In the early compound microscopes the 



i .I.E. M.S. 1900, p. 165. 



