286 



SCIENCE 



[N. S. Vol. XLIX, No. 1264 



iarly his own field, and is in fact a develop- 

 ment of the past six years. It is a distinctive 

 contribution of the British school of aerog- 

 raphers. We may explain that the balance 

 between pressure and velocity of air flow, or 

 what is known as the strophic balance, leads 

 to an equation for the gradient wind of the 

 following form : 



s = 2avp sin (f> ± v'^p cot r/E 



The first term in the right-hand member of 

 the equation represents velocity due entirely 

 to the earth's rotation and hence is known as 

 the geostrophic wind. The other is known as 

 cyclostrophic. Only a few months ago J. S. * 

 Dines called attention to a rather remarkable 

 outcome of this equation, where in the case 

 of a path concave to the " low," velocities of 

 the order of 6m/s for normal counter-clock- 

 wise rotation, and i6in/s for rotation in the 

 opposite direction, appear to be possible. 

 Thus a depression revolving with high speed 

 in a clochwise direction in the northern hem- 

 isphere is dynamically possible. There are 

 reasons why such an eddy on a large scale 

 might not be established or last long, but small 

 area eddies such as those around high build- 

 ings, etc., evidently can be set up with rotation 

 either clockwise or anti-clockwise. This raises 

 the question. How often are dust-whirls, tor- 

 nadoes, and waterspouts observed with a clock- 

 wise rotation? 



Sir Napier Shaw uses as a frontispiece a 

 chart showing paths of the centers of some 

 notable cyclonic depressions of long duration. 

 One is the path of a haguio traced by McAdie 

 from lat. 15° N". in the western Pacific, start- 

 ing on ISTovember 20, 1895, and reaching the 

 Oregon-California coast January 12, 1896, a 

 rather definite duration of 54 days at sea and 

 a probable history of 4 days more in the 

 United States and 5 days over the North At- 

 lantic. Two other long duration storm paths 

 are given. 



These paths of long duration are significant 

 in connection with origin, directive force and 

 persistence of structure of cyclones and anti- 

 cyclones. The most pressing question to-day 

 before aerographers is accurate knowledge of 



the driving forces of a depression, and the 

 directive resultant. There can be no accurate 

 forecasting without this knowledge. 



We are promised three more volumes from 

 the University Press; one, a general survey 

 of the globe and its atmosphere. A second on 

 the physical properties of the atmosphere, and 

 a third, a formal exposition of the dynamics 

 and thermics of the atmosphere. 



Sir Napier Shaw is to be congratulated not 

 only on the output from his o\vn industrious 

 pen, but upon what he has accomplished in 

 stimulating the young men around him, 

 Lempfert, Dines, Gold, Cave, Taylor and 

 others. 



A. M. 



THE NATIONAL ACADEMY OF 

 SCIENCES 



The eleventh number of Volume 4 of the 

 Proceedings of the National Academy of 

 Sciences contains the following articles: 



The " naming Hahits " of the Pulmonate 

 MollusJc Onchidium: Leslie B. Arey and W. 

 J. Orozier, Bermuda Biological Station for 

 Research, Dyer Island, Bermuda. Onchidium, 

 floridanum lives during high tide in "nests," 

 i. e.,,rock cavities, containing a number of in- 

 dividuals. The individuals leave the nest in 

 low water to feed, and return simultaneously 

 to it before the tide rises again, giving evi- 

 dence of homing behavior. 



Growth and Duration of Life of Chiton 

 Tuberculatus : W. J. Crozier, Bermuda Bio- 

 logical Station for Research, Dyer Island, Ber- 

 muda. The growth curve is obtained on the 

 assumption that the age of a chiton may be 

 estimated from the growth-lines upon its shell. 

 The mean duration of life is probably a little 

 less than eight years. 



Groiuth of Chiton Tuherciilatus in Different 

 Environments: W. J. Crozier, Bermuda Bio- 

 logical Station for Research, Dyer Island, Ber- 

 muda. Growth curves obtained under different 

 conditions are compared. 



The Interferometry of Vibrating Systems: 

 C. Barns, Department of Physics, Brovm Uni- 

 versity. The high luminosity of the achrom- 

 atic interferences and the occurrence of but 



