362 sci6:nce progress 



Moore, A. F., and Abbott, L. H., The Brightness of the Sky, Smithsonian 



Miscell. CoUns., 71, No. 4, 1920. 

 Kapteyn, J. C, AND Van Rhijn, P. J., On the Distribution of the Stars in 



Space, especially in High Galactic Latitudes, Astroph. Journ., 52, 23, 



1920. 



METEOROLOGY. By E. V. Newnham, B.Sc, Meteorological Ofi&ce, Air 

 Ministry, London. 



Preliminary Steps in the making of Free-air Pressure and Wind 

 Charts, by C. Le Roy Meisinger {Monthly Weather Review, May 

 1920, vol. xlviii, No. 5). 



In this paper an attempt is made to find for three American 

 stations the most probable mean temperature up to a given 

 level in the free air, when the temperature and direction of the 

 wind on the ground only are known. Should it be possible to 

 do this with reasonable accuracy, isobars might be drawn for 

 various heights, and the problem of forecasting the wind in the 

 free air might be approached more directly than by the method 

 at present in use, in which isobars drawn for sea-level are made 

 use of, together with a certain amount of direct information 

 about the upper winds. It is true that the wind theoretically 

 required to balance the horizontal gradient of pressure at the 

 surface, though not found at the surface because of friction 

 with the ground, often prevails at 500 metres or i ,000 metres, 

 and sometimes at even higher levels, but this is only because 

 the horizontal pressure gradient frequently changes very little 

 up to moderate altitudes. It would be more satisfactory to 

 begin by drawing the isobars in the free air, and then to proceed 

 to calculate the corresponding wind. A knowledge of the 

 direction of the wind would be of little use in North- West 

 Europe for estimating free-air temperatures, but in America 

 there is a much closer connection between the two. 



The three stations employed in this research were Mount 

 Weather (Virginia), Drexel (Nebraska), and Ellendale (North 

 Dakota), 3,000 kite records of free-air temperature being avail- 

 able. The mean temperature of the air-column from the 

 surface up to 2,000 metres height was tabulated for a large 

 number of cases. The results were classified according to the 

 wind direction for each month of the year. It was found that 

 these differences depended to a marked degree upon the direction 

 of the wind, the N.W. winds on the whole bringing cold air, 

 and the S.E. winds warm air, but this effect was much interfered 

 with by another factor, namely the seasonal variation of tem- 

 perature. For instance, in the case of Ellendale, which is 

 at a great distance from the sea, the differences in January are 

 all positive, so that the mean temperature up to 2,000 metres 

 is greater than the surface temperature for all wind directions. 



