11 



SCIENCE-ADVERTISEMENTS 



W. Watson & Sons, Ltd. 



BRITISH MADE 



STUDENTS MICROSCOPES 



The "Praxis" Stand is the Student's model par ex- 

 cellence. Made throughout with the same accuracy 

 and finish as on 

 Watson's highest 

 priced Stands. 

 A fevir special points 

 are: — Standardiza- 

 tion so that addi- 

 tional movements 

 may be fitted as re- 

 quired. Lever fine 

 adjustment. Con- 

 structed of twro solid 

 castings and indes- 

 tructible. All parts 

 are slotted and 

 sprung to compen- 

 sate for vifear. 



Price for Stand only 

 £4. 0. 0. 



Catalogue of Microscopes andJAccessories for 

 all purposes gratis on request from 



W. WATSON & SONS, Ltd. 



Established 1837 

 313, High Holborn, London, England 



Send for descriptive circulars and sample 

 pages 



PRINCIPLES OF 



STRATIGRAPHY 



BY 



AMADEUS W. GRABAU. S.M., S.D. 



PROFESSOR OF PALAEONTOLOGY IN 

 COLUMBIA UNIVERSITY 



Large Octavo, 1150 pages, with 254 illustrations in the text. 

 Cloth bound, price, $7.50. 



Send for descriptive circular 



A. G. SEILER & CO. 



PUBLISHERS 

 1224 Amsterdam Avenue NEW YORK. N. Y. 



