^54 TttS AMERICAisr MONI^HLY [Aug 



F. Shilling-ton Scales, F. R. M. S. in Science Gossip 

 says : Our object is to make this column as interesting- 

 and as helpful as possible to our readers, by keeping them 

 informed of various matters of interest in the microscop- 

 ical world, especially with reference to methods of work. 

 We propose in future to lay g-reater stress, from time to 

 time, upon the improvement of the microscope and its ac- 

 cessories. We desire, in fact, to make this column a valu- 

 able record of the progress of the microscope, of new or 

 modified stands, objectives, apparatus, etc. The present 

 keen competition amongst opticians, especially amongst 

 the limited few who are in the front rank, and with whom 

 workers are mostly concerned, gives rise to constant pro- 

 gress. It will be our endeavour to keep our readers ad- 

 vised on these points without fear and without favor. 



laOEOSCOPICAL APPARATUS. 



New Achromatic Condenser. — Although the Abbe Con- 

 denser, or, as it is often called. Illuminator, is recog-nized as 

 being suitable for most g-eneral practical work, mainly on 

 account of its being easy to use, yet for more critical work 

 a well eorrected condenser becomes a necessity. Messrs. 

 Beck have broug-ht out a new condenser in hig-h-power work 

 that is achromatic and has a numerical aperture of 1 N. A. 

 This is the maximum that can be obtained without having- 

 the front of the condenser in immersion contact with the 

 under surface of the slide, and its aplanatic aperture ex- 

 ceeds '9 N. A. It is thus greatly superior to the ordinary 

 Abbe Illuminator. The front lens is removable to make a 

 low-power condenser. An Iris diaphragm and a swinging 

 arm, with rotating fitting for colored glasses, or stops, are 

 provided. A bracket is ingeniously added at the bottom of 

 the mount, into which the optical portion may be screwed, 

 and the whole condenser thus reversed. This is often a 

 convenience. The price of the complete condenser is $15 

 but with Iris dirphrag-m only $12. 



New Tripple Nosepiece.— The Messrs. Beck have also 



