1900] MICROSCOPICAL JOURNAL. 253 



be strongly recommended. Then set to work, making up 

 your mind to overcome the many difficulties which are 

 sure to occur before proficiency is reached. — Annual of 

 Microscopy. 



Notes on Microscopy. 



F. SHILLINGTON SCALES, F.R.M.S. 



New 1-12in. Immersion Objective. — Messrs. R. and J. 

 Beck have sent for ourinspection a new 1-12 in. immersion 

 objective with a numerical aperture of 1.4 and an aplan- 

 atic cone of 1.35 N. A. It is perfectly achromatic, and 

 the makers modestly and rightly claim no more than this, 

 but we can speak highly of the performance of the lens. 

 It is exceptionally free from color, the definition is excel- 

 lent, and the increased quantity of light passed is most 

 noticeable. It bears comparatively high eye-piecing well. 

 The working distance is of course rather less than in ob- 

 jectives of lower aperture. The price brings it within the 

 reach of all workers requiring an objective of this descrip- 

 tion, being $40, or $48 with correction collar. 



New Immersion Condenser. — Competition between 

 the opticians grows apace and the worker and the ama- 

 teur benefit accordingly. Messrs. Beck have brought out 

 a new immersion condenser, which we commend herewith, 

 with a numerical aperture of 1.36 to 1.4, and an aplanatic 

 cone of 1.3 N.A. The combination consists of four sys- 

 tems of lenses, the front of which is a hemisphere with 

 three combinations behind, and constructed on the prin- 

 ciple of an oil-immersion objective. By the courtesy of 

 the makers we have had an opportunity of testing this 

 condenser in connection with the objective 1.4 N.A. 

 above described and are much pleased with its perform- 

 ance. The working distance is 0.6 in. By an ingenious 

 arrangement the optical part of the condenser can be re- 

 versed in the mount so that it may be used with micro- 

 scopes fitted with under-stage fitments instead of the 



