SCIENCE-ADVERTISEMENTS 



Longrnans' ISew Books 



'J^vers and Estuaries ; or. Streams and Tides 



An Elementary Study. By W. Heney Huntkb, M.Inst.C.E., M.Am.Soc.C.E., Consulting 

 Engineer to the Manchester Sbip Canal, etc. With 8 diagrams. 8vo. $1.00 net. (Weight 12 02.) 



A study of the natural forces to which rivers and estuaries owe their being and their form, and 

 of modern examples of engineering works carried out for the regulation of the features which result 

 from the operations of these forces ; as well as for the improvement of the rivers, in respect of flood 

 discharge and navigation. 



Theory and Calculation of Electric Currents 



By J. L. LaCour, Vesteras, and O. S. Beagstad, Trondhjem. Translated by Stanlbt P. 

 Smith, D.Sc, Assoc. M.Inst.C.E., A.M.I.E.E., London. With 404 diagrams. 8vo. Pp. xii4-482. 

 S5. 00 net. ( Weight 50 oz. ) 



Mechanics of Particles and Rigid bodies 



By J. Prescott, M.A., Lecturer in Mathematics in the Manchester School of Technology, and 

 Assistant Lecturer in the University of Manchester. With 219 diagrams. 8vo. Pp. viii-f536. 

 $3.50 net. (Weight 38 oz. ) 



In this book there are chapters on Elasticity, Bending of Beams, the Problem of two or more 

 Bodies, and Spinning Tops, as well as a short appendix on Conic Sections. It contains about 600 

 examples, many of which are culled from University and other examination papers, and the answers 

 to the questions are given. 



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Longmans, Green, & Co. 



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4th Ave. & 30th St., N. Y. 



Leltz Research 

 Microscope Stand 

 "AA" vnth New 

 Rotary Mechan- 

 ical Stage and 

 Apochromatic 

 Objectives. 



UNITED STATES 

 BRANCH 



For Research 



Leit z Apochromatic Objectives 



[ in conjunction with^ 



Universal Microscope Stand "AA" 



A microscope equipped for[critical'work[should be available in every 

 research laboratory. 



The Apochromatic Series of Leitz objectives is now constructed 

 under a revised optical data and found to excel all others in flatness 

 of field, high degree of color correction and resolving power. Sub- 

 jected to critical examination and comparison, they are selected by 

 the Government Research Laboratories and for Research in the 

 Leading Educational Institutions. 



Our Universal Microscope Stand "AA" has been adopted as Standard 

 for research. This microscope features the Leitz side fine adjust- 

 ment, recognized as the most sensitive, at the same time proving 

 greatest stability. Our New Rotary Mechanical Stage is supplied 

 for critical research and photo-micrography, making Stand "AA" to 

 represent the highest type of Research Microscope obtainable. 



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