220 THE AMERICAN MONTHLY. [September. 



three dimensions, and to make use of certain terms and symbols intro- 

 duced by Hamilton, such as scalar^ tensor^ with its symbol T^ etc. 



Though based upon the principles and methods of Grassman, the 

 work contains much matter that is believed to be original with the 

 author, while a large number of exercises have been inserted in the be- 

 lief that the repeated application of principles to the solution of actual 

 problems is the true basis for acquiring a command of any branch of 

 mathematics. The book richly deserves the attention of all interested 

 in the science. 



Handbook of English History. By E. H. Gurney. i6°, 144 pp. 

 Ginn & Co., Boston. (Price, 85 cents.) 



This little work designed as a reference handbook for readers, students, 

 and teachers of English history, can hardly fail to gain recognition. 

 Mr. Gurney exercised great care in compiling his materials and suc- 

 ceeded in producing in a con^pact form a work that identifies every 

 prominent man of English history from the time of the Confessor to 

 Victoria, giving the date of his death, to whom married, and the num- 

 ber and names of his children. Thus by enabling the student to trace 

 the connection of the characters about whom he is reading saves hours 

 of study and makes his work a pleasure. 



The materials for this work havfe been drawn from Dugdale, Free- 

 man, Palgrave, Longmann, Sandford, and Townsend, and many other 

 valuable works, and the whole passed through a critical examination 

 and comparison. 



SUBSCRIBERS' NOTICES. 



[These notices will be given six insertions in this column at 25 cents per line or fraction thereof. 

 FOR EXCHANGE.— Slides of selected diatoms. D. B. WARD, Poughkeepsie, N. Y. 



OFFERED. — Diatomaceous Earth from Utah (Desert) for Histological Mounts. 



% PROF. ORSON HOWARD, Salt Lake City, Utah. 



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WANTED. — Any works on Microscopy not already in my Library. 



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WANTED. — A clean copy of Wolle's Fresh- Water Algse of the United States (2 vols.) ; also good 

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FOR SALE CHEAP. — New Gundlach y^g homogeneous immersion objective, for ^"^ glycerine or 

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FOR SALE. — Beautiful photo-micrographs of P. angulatum. Only 2=; cents each. 



J. E. BAKER, M. D., Wyoming, Ohio. 



WANTED.— Proceedings Am. Acad. Sciences, XI, 1876. 



C. W. SMILEY, Washington, D. C. 



FOR SALE OR EXCHANGE.— Mosquitoes, male and female. Price 75 cents each. Will ex- 

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A $5 MICROSCOPE. — Made on proper scientific principles. Magnifies ico diameters or 10,000 • 

 times. For other interesting articles send for list of Popular Scientific Specialties. 



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