SCIENC 
SINGLE COPIES, 15 CTs. 
a = ie 261. FRIDAY, DECEMBER 29, 1899. ANNUAL SUBSCRIPTION, $5.00 
HIGH-CLASS INSTRUMENTS 
Several months ago I disposed of my Philadelphia plant, patterns, jigs, 
merchandise, etc., and removed my business to this city where an entirely 
new shop, several times the size of my old one, with new tools, has been es- 
tablished for the manufacture of ‘‘ Willyoung Apparatus.’’ Every drawing 
has been thoroughly overhauled and every possible improvement has been 
made. Being thus absolutely unfettered by any old stock to work off, or 
parts to work in, I feel that I can offer absolutely unsurpassed instruments 
to my patrons. 
zi : Catalogue W, just issued, is the most complete and logically arranged 
Willyoung 8/7 to 15’7-110 Volt thing of its kind ever issued. Sent free to colleges and laboratories. You 
X-Ray Machine. deal direct with the manufacturer. No selling agents. 
ELMER G. WILLYOUNG, 82-84 Fulton Street, New York City 
JOHN WILEY & SONS’ busucarions 
Statistical Methods with Special Refers | Kinematics of Machinery 
ence to Biological Variation By Joun H. Barr, Professor of Machine Design, 
Intended especially for those interested in the quan- Sibley College, Cornell University Over 200 figures. 
titative study of species and of organic variation. 250 pages. 8vo, cloth, $2.50. 
By C. B. Davenvorz, Assistant Professor of Zoology Ss : 
_at the University of Chicago. 148 pages. 16mo, Heat and Heat-Engines 
morocco, $1.25. A Study of the Principles which Underlie the Me- 
chanical Engineering of a Power Plant. By Frep- 
The Cost of Living as Modified by Sani- ERICK Remsen Hurron, E.M., Ph.D., Professor of 
tary Science Mechanical Engineering at Columbia University. 
i : 559 pages. 8yo, cloth, $5.00. 
By Eien H. Ricwarps, Instructor in Sanitary 
Science in the Massachusetts Institute of Technology. Water-Supply Engineering 
) : 
TES BEE NEE ea ge The Designing, Construction, and Maintenance of 
6 5 Water-Supply Systems, both City and Irrigation. 
Handbook on Testing Materials By A. Prescorr Fotwetu. S8vo, cloth, 575 pages, 
For the Constructor. Methods, Machines, and Profusely Illustrated, $4.00. 
Auxiliary Apparatus. By Apotr Marrens, Profes- 
sor. Authorized translation and editions by Gus. C. | The Filtration of Public Water-Supplies 
Henning (M.H., Stevens, ’76). 2 vols., Svo, cloth B ¢ gad 
2 ; , y ALLEN Hazen. 3d edition greatly enlarged and 
100) pages and plates, $7.50. brought up-to-date. S8vo, cloth, 350 pages, fully 
ae i i illustrated, $3.00. 
Determination of Radicals in @arbon Tapia ed 2-00 
Compounds Manual of Practical Assaying 
By Dr. H. Meyer, Imperial and Royal University, By H. Van F. Furman. 5th edition, December, 
Prague. Authorized translation by J. Bishop Tingle, 1899, bringing the work quite abreast of the latest 
Ph.D., F.C.S., Instructor of Chemistry at the Lewis investigations and discoveries in the subject treated. 
Institute, Chicago. 12mo, cloth, $1.00. 8vo, cloth, viii + 463 pages, $3.00. 
Order through your bookseller, or copies will be forwarded postpaid by the publishers 
on the receipt of the retail price 
JOHN WILEY & SONS, 53 East 10th Street, New York 
