The Microscopist's Annual for 1873. 



Contains List of all the Microscopical Societies In the 

 country, with names of officers, days of meeting, etc. ; 

 etc. ; Alphabetical and Classified Lists of all the Manu- 

 facturers of Microscopes and Objectives, Dissecting Ap- 

 paratus, Microscopic Objects, Materials for Microscopists, 

 in Europe and America, etc., etc. ; Postal Hates, Eules 

 and Regulations, prepared expressly for microscopists ; 

 Weights and Measures, with tables and rules for the con- 

 version of different measures into each other; Custom 

 Duties and Eegulations in regard to Instruments and 

 Books ; Value of the Moneys of all Countries in U. S. 

 Dollars ; Value of the Lines on Nobert's Test Plates ; 

 Table of Moller's Probe Platte, with the number of lines 

 to inch on the several diatoms, etc., etc. ; Focal Value 

 of the Objectives of those makers who Number their 

 Objectives (Hartnack, Nachet, etc.) ; Focal Value of the 

 Eye-pieces of different makers ; Magnifying Power of 

 Eye-pieces and Objectives, etc., etc. The whole form- 

 ing an indispensable companion for every working micro- 

 scopist. Limp Cloth, Gilt - - 25 cents, 



J83- The " Annual " for 1880 is in a forward state of preparation, and 

 will be uniform in size and price with that for 1879. 



Microscope Objectives. 



The Angulai Aperture of Microscope Objectives. By 

 Dr. George E. Blackham. 8vo., Cloth. Eighteen full 

 page illustrations printed on extra fine paper. $1.25. 

 Sold only by Subscription. 



This is the elaborate paper on Angular Aperture, read by Dr. 

 Blackham before the Microscopical Congress, held at Indianapolis. 



Kutzing on Diatoms. Nearly ready. 



The Siliceous Shelled Bacillarise or Diatomaceae; the 

 History of their Discovery and Classification ; their Dis- 

 tribution, Collection, and Life-History. By Friedrich 

 Traugott Kutzing. Translated from the German by Prof. 

 Hamilton L. Smith, of Geneva, N. Y. 12mo., Cloth, 

 Gilt, ------ 50 cents. 



