SCIENCE.— AD VERTISEMENTS. 



X-Ray Apparatus. 



Almost invariably when a purchaser makes inteUi- 

 gent comparison of different X-Eay "outfits" on the 

 market, we receive his order. There must be reason 

 for this ; and for this reason we simply ask intending 

 buyers to carefully investigate the merits of our appa- 

 ratus. To begin with, send 2c. stamp for 24-page illus- 

 trated catalogue No. 185, and after reading it write 

 us fully concerning your individual requirements. 



We also handle Electrical Measuring Instruments, Physical 

 Apparatus, Psychological Apparatus, Storage Batteries, etc., 

 making a specialty of "Daly Free'' importations from the 

 best European Manufacturers. Correspondence invited. 



James Q. Biddle, 



Dealer, Manufacturers' Agent and Importer, 



909 Drexel Building, Philadelphia. 



RARE MINERALS. 



THAUMASITE, from Paterson, N.J. , a sulphate, silicate and 

 carbonate of calcium, pure white, 25c. 



EKDEMITE, bright yellow on red wulfenite, Arizona, 50c. 



Collections for Schools, 



ALPHA COLLECTION, twenty-five specimens in trays, con- 

 tained in a neat wooden box and accompanied by a U6- 

 page guide book {XIII., Guide tor Science Teaching, Bos- 

 ton Society of Natural History), Frice, complete, $1.00. 



CABINET COLLECTIONS, 100 specimens, small size, $5.00. 

 100 specimens, large size, $10.00. These specimens are 

 each accompanied by a label giving name, system of 

 crystallization, chemical formula, and locality, and make 

 a good working collection for a student. 



EXCELSIOR COLLECTION for high schools and colleges. 

 200 specimens, nicely mounted on wooden blocks, with 

 beveled fronts for receiving labels. Price, packed, 

 $100.00. Hchool Bulletin }\i^t out. 



Loose Crystals. 



Small packages of free crystals for crystallographic study 

 may be sent for inspection by mail at small cost. Ap- 

 proval boxes of cabinet specimens by express or freight. 



ROY HOPPING, 



MINERAL DEALER, 



504=506 Liberty Building, 

 Liberty and Greenwich Sts. 



NEW YORK. 



Horsford's Acid Phosphate 



Is the most effective and agreeable 

 remedy in existence for preventing in- 

 digestion, and relieving those diseases 

 arising from a disordered stomach. 



D. W. W. Gardner, Springfield, Mass., 

 says: " I value it as an excellent preventive of 

 indigestion, and a pleasant acidulated drink 

 when properly diluted with water and sweet- 

 ened." 



Descriptive pamphlet free on application to 

 Rumford Chemical Works, Providence, R. I. . 



Beware of Substitutes and Imitations. 



For sale by all Druggists. 



Tlie Thomas A. Scott Fellowship in Hygiene,. 

 University of Pennsylvania. 



Tbe Scott Fellowship in Hygiene at the University of Penn- 

 sylvania falls vacant October 1st, 1897. Individuals desirous- 

 of applying for appointment to the position can obtain de- 

 tails of the governing regulations by communicating with 

 Prot. A. C. Abbott, Director of the Laboratory of Hygiene, 

 University of Pennsylvania, Philadelphia. 



Dec. 



1896. Just Published. Sixth Edition of 



THE MICROSCOPE ^SSu%^T?.l'bT- 



By SIMON HENRY QAQE, Professor of Microscopy. His- 

 tology and Embryology in Cornell University and the 

 New York State Veterinary College, Ithaca, N. Y., U.S A. 

 Sixth edition, rewritten, greatly enlarged, and illustrated, 

 by 165 figures in the text. Price, $1.50, postpaid. 



COMSTOCK PUBLISHING CO., Ithaca, N. V^ 



NEW CATALOGUE. 



We have recently issued a new edition, revised and en- 

 larged to 64 pages, of our catalogue of 



Books on Chemistry, Clienaical 

 Teclinology in Pbysics. 



It is arranged by subjects, and includes all the standard 

 books in Chemical and Physical Science, as well as the re- 

 cent 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, 



