616 EXPERIMENT STATION RECORD. [Vol 40 



Past and present climates of our leading crop plants, H. C. Cowles (V. S. 

 Mo. Weather Rev., 46 (1918), No. 11, p. 521).— A paper presented at the Balti- 

 more meeting, 1918, of the Association of American Geographers is summarized 

 as follows: 



" Most crop plants have originated in what are now tropical or subtropical 

 regions ; tropical America, Malaysia, and the Levant. The potato alone of the 

 major crops came from a cool region. Many of the crups are now grown only 

 outside the Tropics, while others are still raised in their original zone. It is 

 generally agreed that mutation, or perhaps acclimatization, rather than change 

 of climate, is responsible for the change of habitat of most of our crop plants, 

 while the rest have not moved. An interesting phase of plant origin is that for 

 many the place of origin is by far not the best habitat for that plant. A cold- 

 resistant plant is as likely to originate (though not as likely to survive) in a 

 warm as in a cold region." 



Some recent contributions to the physics of the air, W. J. Humphreys 

 (Science, n. ser., 1$ (1919), Nos. 1259, pp. 155-148; I860, pp. 18£ 188, fins. 6: 

 abs. in U. S. Mo. Weather Rev., 46 (1918), No. 12, pp. 563-566).— This consists 

 of extracts from the vice-presidential address, physics section, of the American 

 Association for the Advancement of Science, at the Baltimore meeting, 1918. re- 

 viewing the present status of knowledge and research with reference to the 

 temperature of the free air, isothermal state of the upper air, storm effects on 

 temperature gradients, the law of wind Increase with elevation, barometric 

 fluctuations, and atmospheric electrical phenomena. 



Seasonal precipitation (17. 8. />»/''• Ayr., Nat. Weather and Crop Bui. No. 2 

 (1919), p. 2, fig. 1). — A chart is given winch shows the percentage of the 

 normal precipitation of the United States which occurred from September 1, 

 1918, to February 28, 1919. 



"The total precipitation for this period was above normal throughout nearly 

 all Of the Gulf States, and also <>\or the Oreat Plains region, the central Rocky 

 Mountain districts, and the central Plateau and Pacific Coast States. Else- 

 where it was mostly below normal, particularly along the Atlantic seaboard, 

 in portions of tin 1 Ohio Valley, the far Southwest, and far Northwest. In the 

 central Plains region and some of the central Qnht districts the totals were 

 more than one and one-half times the normal, but in some sections of the 

 Southwest and Northwest but little more than half the usual amount for this 

 period was received." 



The dustfall of March 9, 1918, A. N. Winchei.l and EL R. Miuh; iAmcr. 

 Jour. Soi., 4. ser., 46 (1918), No. 274, PP- 599-609, figs. 8; Set Auur. Sup., 87 

 i 1919), No. 9858, pp. 284, 855, figs. 2).— A study on this dustfall, made at Madi- 

 son, Wis., is reported, from winch the authors conclude that "a single storm 

 may transport a million tons of rock material a thousand miles or more," thus 

 emphasizing the importance of the wind as a geological agent. In their opinion 

 "it is an open question whether the total work done by the air in transporting 

 rock material is not of the same order of magnitude as the work of the same 

 kind accomplished by water. 



" It is clear that arid regions will constantly lose rock material by wind 

 action and that the dust will be held by moist areas Which are covered by 

 vegetation. . . . The soil of any region is probably derived in considerable 

 part from material transported by the wind. Diatoms and all sorts of plant and 

 animal life of microscopic size as well as fragments of larger organisms may 

 be transported long distances by the wind." 



The dustfalls of March. 1918, A. N. Win. i.kll and E. R. Miiiik [U. B. 

 Mo. Weather Rci\, 46 (1918), No. 11, pp. 502-306, figs. S).— This article supple- 



