SCIENCE-ADVERTISEMENTS 



THE 

 PRINCIPLES OF 

 STRATIGRAPHY 



BY 

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



PROFESSOR OF PALEONTOLOGY IN 

 COLUMBIA UNIVERSITY 



"Should be on the reference shelf of every col- 

 lege, normal achool, and large high school in the 

 United States." — Journal of Geography, Vol. XIII. 

 Jan. 1915. 



8vo, IJSO pases, 264 illattration*. Prie; $7.S0 



Dascriptiva Circular Sent upon Reqaett 



A. G. SEILER & CO. 



NEW YORK CITY 



The great formal methods of analysis 

 are essential alike to the practical and to 

 the pure mathematician. To confirm and 

 extend the student's knowledge of these 

 methods is the chief aim of 



Advanced Calculus 



By EDWIN BIDWELL WILSON 



Professor of Mathematics in the Massachusetts Insli- 

 iaie of Technology 



It also gives modern rigorous tendencies due 

 attention and supplies in a single volume a com- 

 prehensive second course in calculus. To connect 

 with elementary texts there are two chapters in 

 review, and many subsequent chapters are tempered 

 with material which is essentially review. Ad- 

 vanced differential calculus is represented by work 

 on Taylor's formula, with special reference to 

 approximate analysis, partial differentiation of expli- 

 cit and implicit functions, complex numbers and 

 vectors. 



8vo, cloth, 556 pages, $5.00 



Ginn and Company 



Boston New York Chicago London 



Atlanta Dallas Columbus San Francisco 



Announcing the Compton Quadrant Electrometer 



This electrometer, of the quadrant type, somewhat 

 similar to the Dolezalek design, has been developed by 

 Dr. Karl T. Compton and Dr. Arthur H. Compton at 



Princeton University. 



The instrument is highly sensitive (0-50,000 mm. per 

 volt), needle and quadrants are well insulated, the capacity 

 is exceptionally small (about 15 cm.) and the reflections 

 are proportional to the voltages throughout a very wide 

 range. A conducting quartz suspension is used, which 

 yields a period of 2 to 5 seconds at low sensitivities. It 

 is practically dead beat. 



We have secured the exclusive manufacturing and 

 sales rights to the Compton Electrometer. It is described 

 in Circular No. 6, which also quotes prices. Write for it. 



PYROLECTRIC INSTRUMENT CO. 



PYROMETRIC AND ELECTRICAL PRECISION INSTRUMENTS. 

 148 East State Street TRENTON, N. J. 



E. F. NORTHRUP, President and Technical Adviser. 



