ii SCIENCE.—ADVERTISEMENTS. 
NEW SCIENTIFIC BOOKS—Just Ready or in Press 
The Liquefaction of Gases 
Just Ready. Irs RisE AND DEVELOPMENT. Cloth, 12mo, $1.50. 
By Witierr LepLey Harptn, Harrison Senior Fellow in Chemistry in the University of Penn- 
sylvania. 
A complete history of the development of the methods employed in the liquefac- 
tion of gases, as the following clipping from the preface will show : 
Popular “Recent developments in the liquefaction of air and the recent liquefaction of hydro- 
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Industrial The various forms of apparatus are shown in illustrations. In addition to the history 
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of the gaseous and liquid states of matter, and the theory of the regenerative method of 
refrigeration are also considered. In the conclusion, a brief outline is given of researches 
at low temperatures and of the industrial application of liquefied gases. 
THOMPSON—Light Visible and Invisible. 
A Series of Popular Lectures delivered by SYLVA- 
nus P. THompson, D.Sc., M.R.I., F.R.S., author 
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BURBURY—A Treatise on the Kinetic 
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F.R.S., late Fellow of St. Johns, Cambridge. 
8vo, Cloth. Price, $2.00 net. 
Cambridge University Press. 
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A list of all species described in North America 
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SUTER—Handbook of Optics. For Stvu- 
DENTS OF OPHTHALMOLOGY. By WILLIAM NoR- 
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National University, and Assistant Surgeon, Epis- 
copal Eye, Ear and Throat Hospital, Washington, 
D. C. Cloth, 16mo, $1.00 net. 
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LANGE—Our Native Birds. How To PrRo- 
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LENGFELD—Inorganic Chemical Prepa- 
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Chicago. Cloth, 16mo, 60 cents net. 
This book gives directions for making about fifty 
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Blowpipe Analysis 
By FreDERICK Hurron GEeTMAN, Instructor in Chemistry in Stamford High School. Cloth, 
16mo. Just Ready. 60 cents net. 
This little book is designed for use in high schools, and also to serve as an aid to college students in 
the study of qualitative analysis. 
THE MACMILLAN COMPANY, Publishers, New York. 
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