20 



SCIENCE 



[Vol. LV. No. 1410. 



this admirable work and hope that more is in 

 store for us. 



We, who are about to be shelved, used to 

 live in this countrj', peacefully under the con- 

 stitution and we were quite happy in our sim- 

 plicity. One day a man by the name of Ein- 

 stein came along and mixed that constitution 

 up. We were told that it had long been an anti- 

 quated document anyway. There were diffl- 

 culties, but eventually we managed to fit in; 

 for they had left us, at least, with the doctrine 

 of energy. Now, I read that the classical law 

 of the conservation of energy must also go, 

 that at best it is only statistical like the second 

 law of tliermodynamics. Truly these young 

 bloods are Balkanizing the Avhole of physics 

 and our ancient constitution has gone the way 

 of the mark. 



Gael Barus 

 Brown University 



SCIENTIFIC BOOKS 



Trees of Indiana. By Charles C. Deam, 

 State Forester of Indiana. First revised 

 edition. 317 pages; 137 plates. Publica- 

 tion 13 of the Department of Conservation, 

 State of Indiana. April, 1921. 



The forerunner of the present work, under 

 the same title and by the same author, was 

 issued in 1911. So great was the demand for 

 that book that the edition of 10,000 copies 

 lasted only three years, while a second edition, 

 printed in 1919', was exhausted within iive days 

 of publication. The present "first revised edi- 

 tion" is fundamentally a new work, with new 

 illustrations and completely rewritten text. 



During the past decade nmnerous "tree 

 books" have been issued by various state or- 

 ganizations, bu-t it is doubtful if any of these 

 contain more original matter than the present 

 work. Certainly none of them contain more 

 loteal color. The botanical descriptions are 

 based on Indiana material, and the illustra- 

 tions are photographed from Indiana speci- 

 mens, while the distributional peculiarities in 

 Indiana of the various species are treated in 

 gratifying detail. It is in this latter particular, 

 perhaps more than any other, that the book 

 will prove of service to the general botanical 



public. In the course of his studies of the 

 flora of Indiana, the author, within the last 

 ten years, has traveled more than 27,000 miles, 

 by auto, and has visited every county and tra- 

 versed practically every township in the state. 

 As a result he is able to present, at first hand, 

 a wealth of detail in regard to local tree dis- 

 tribution, not to mention various other observa- 

 tions which bespeak intimate familiarity with 

 the tree flora of the state. The attention given 

 to the ecological relations of the different spe- 

 cies is especially worthy of note, and this 

 feature alone will recommend the work to a 

 wide circle of readers. 



George E. Nichols 



NOTES ON METEOROLOGY AND 

 CLIMATOLOGY 



SKY BRIGHTNESS AND DAYLIGHT ILLUMI- 

 NATION 



What is the relation between sky brightness 

 and the electric light load carried by the central 

 lighting plant 1 How much sky-light will be cut 

 off by a row of buildings on the opposite side 

 of the street These questions and many others 

 may be solved by studies of the brightness of 

 the sky and daylight illumination such as have 

 been carried out by Dr. H. H. Kimball, of the 

 Weather Bureau at Washingtop. The prac- 

 tical utility of such investigations is attested 

 by the interest shown by illuminating engi- 

 neers, architects and electrical engineers. A 

 paper, recently appearing in the Monthly 

 Weather Beview,^ summarizes with considera- 

 ble detail a report submitted to the Illuminat- 

 ing Engineering Society, of whose committee 

 on sky brightness Dr. Kimball is chairman. 



The observational program which has been 

 followed in making the measurements has been 

 to make jihotometric readings with a Sharj)- 

 Millar photometer at elevations of 2°, 15°, 30°, 

 45°, 60°, 75° and 90° above the horizon on ver- 

 tical circles at azimuth intervals of 45° begin- 

 ning with the sun's vertical and proceeding 

 half-way around the horizon. Onl3r half the 

 sky is measured because it is assumed that the 



1 Kimball, H. H., and Hand, I. R. : Sky bright- 

 ness and daylight illumination measurements. 

 Sept., 1921, pp. 481-48S. 



