If\ 



SCIENCE 



Friday, October 21, 1898. 



Single Copies, 15 cts. 

 Annual Subscription, S5.00' 



General Electric Co.'s 



New X=Ray Tube 



WITH AUTOMATIC VACUUM REQULATOR. 



Simple. Efficient. Long-lived. Cannot run too high in vacuum. 



Roentgen Ray Apparatus, catalogue No. 9,050. Minia- 

 ture, Candelabra, Decorative Lamps, catalogue No. 9,044. 



(.GENERAL. ELECTRIC COMPANY.) 



HARRISON. N. J. 



NEW BOOKS AND NEW EDITIONS 



Text-Book of Geodetic Astronomy 



By John F. Hayfoed, C.E. 8vo, cloth, §3.00. 



Tlie Tlieory of Electrical Measurements 



By William A. Anthony, Professor of Physics. 

 12mo, cloth, $1.00. 



Tbe Elements of Sanitary Engineering 



By Prof. Mansfield Mebeiman. 8vo, cloth, 

 $2.00. 



A Text-Book of Volumetric Analysis 

 with Special Reference to the Volu- 

 metric Processes of the Pharmaco- 

 poedia of the United States 



Designed for the Use of Pharmacists and Pharma- 

 ceutical Students. By Henry W. Schimpf, Ph.G., 

 M.D. Rewritten and Reset. 12mo, cloth, $2.50. 



A Text-Book of Mineralogy Tvith an 

 Extended Treatise on Crystallogra- 

 phy and Physical Mineralogy 



By Edward Salisbury Dana. New Edition, 

 entirely Rewritten and Keset. With nearly 1,000 

 figures and a colored plate. 8vo, cloth, $4.00. 



Thermo- Dynamics of the Steam-Engine 

 and Other Heat Engines 



By C. H. Peabody. 4th Edition. Rewritten and 

 Reset. 8vo, cloth, $5.00. 



Manual of Determinative Mineralogy 



With an Introduction of Blowpipe Analysis. By 

 George J. Brush. Revised and enlarged, with 

 entirely new tables for the identification of min- 

 erals. By Samuel L. Penfield. Fifteenth 

 Edition. 8vo, cloth, $4.00. 



JOHN WILEY & SONS, 53 E. 10th St., New York City 



