SCIENCE.— AD YER TISEMENTS. 



NEW VOLUME OF 



The Century Science Series 



Edited by SiE Henky E. Roscoe, D.C.L., F.R.S. 

 12mo, Cloth, each $1.25. 



JAMES CLERK MAXWELL 



AND MODERN PHYSICS, 



BY R. T. GlazebrooK, F.R.S.. 



Fellow of Trinity College, Cambridge, University Lecturer 



in Mathematics, and Assistant Director of 



the Cavendish Laboratory. 



With Portrait. 12mo, Cloth, $1.25. 



ALREADY PUBLISHED IN SAME SERIES. 



Justus Von Liebig: His Life and Work (1803= 



1873). By W. A. Shenstone, F.I.C. 

 The Herschels and Modern Astronomy. By 



Miss Agnes M. Clerke. 

 Charles Lyell : His Life and Work. By Eev. 



Peof. T. G. Bonney, F.R.S. 

 John Dalton and the Rise of Modern Cheni= 



istry. By Sir Henry E. Roscoe, F.R.S. 

 Major Rennell, F.R.S., and the Rise of English 



Geography. By Clements R. Markham, C. 



B., F.E.S., President of the Royal Geographical 



Society. 



Other volumes in preparation. 



The Elements of Physics, a College Text- 

 Book. By Edward L. Nichols, B. S., Ph. D., 

 Professor of Physics, Cornell University, and 

 William S. Franklin, M.S., Professor of Phy- 

 sics and Electrical Engineering at Iowa Agricul- 

 tural College. To he completed in 3 vols. Now 

 ready — Vol. I. Mechanics and Heat. 8vo, cloth, 

 $1.50 net. 



MACMILLAN & CO., 



66 Fifth Avenue, NEW YORK. 



ALGEBRA SELF-TAUGHT. 



By Dr. Paget Higgs. 

 The best book in the Market. Price, 60 Cents. 



SPON & CHAMBERLAIN, Publishers, 



12 Cortlandt St., New York. 



For Brain-Workers, the Weak and 

 Debilitated. 



Horsford's Acid Phosphate 



is witliout exception, tlie Best Remedy 

 for relieving Mental and Nervous Ex- 

 haustion ; and where the system has 

 become debilitated by disease, it acts 

 as a general tonic and vitalizer, afford- 

 ing sustenance to both brain and body. 



Dr. E. Cornell Esten, Philadelphia, Pa., 

 says : "I have met with the greatest and most 

 satisfactory results in dyspepsia and general de- 

 rangement of the cerebral and nervous systems, 

 causing debility and exhaustion. 



Descriptive pamphlet free on application to 

 Rumford Chemical Works. Providence. R. I. 



Beware of Substitutes and Imitations. 



For sale by all Druggists. 



NB\N CATALOGUE, 



We have recently issued a new edition, revised and 

 enlarged to 64 pages, of our Catalogue of 



Books on Chemistry, Chemical 

 TechnoJogy in Physics. 



It is arranged by subjects, and includes all the 

 standard books in Chemical and Physical Science, a* 

 well as the recent literature up to date. 



A copy of this Catalogue will be sent free by mail 

 to any address. 



D. Van Nostrand Company, 



Publishers and Importers of Scientific Books, 



23 Murray St. and 27 Warren St., New York. 



With eighteen years' experience as manager of the microscopical department of an optical firm, I now ofl'er W 

 S my careful personal attention in supplying first-class ^ 



I OPTIC Ali AND OTHER ?Sl5S™Sir..« I 



f ^-^ Jt JL ^\yax J.^ INSTRUMENTS € 



^ and materials. I desire to make quotations or to give any other information needed. Importations at actual ex- ▼ 

 m penses only, on makers' prices. Edward Pennock, S609 Woodland Ave. {opp. Univ. of Pa.}, Philadetph, 



CABINET SPECIMENS. 



SYSTEMATIC COLLECTIONS. 



^^^^ZZI^^^^^^^Z^ BLOWPIPE MINERALS. 



Our stock is generally admitted to be the finest, most varied and complete in the world. You are, therefore, almost sure 

 to obtain from us any mineral you want. 



Our S'20,000 Systematic Collection received highest award at World's Fair, Chicago, 1893. 



124 pp. Catalogue (16th edition), iHusira^ed by 87 cuts and giving species-number, crystallographic system, hardness, 

 8peciflc gravity, chemical composition and formula of every mineral, 26 cents in paper ; 50 cents in cloth. 



44 pp. Illustrated Price Lists, 4c. Bulletins and Circulars Free. 



GEO. L. ENGLISH & CO., Mineralogists, 64 East 12th Street, NEW YORK CITY. 



MINERALS. 



