340 SCIENTIFIC RECORD FOR 1884. 



from studyiug a system of lines similar to isobars and coustructed in 

 the following manner : If from the center of the earth radii are drawn 

 through the ordinary elliptical isobars we have a system of cones, which 

 can be so cut by a plane that the sections shall be concentric circles; if 

 then we project this system upon the earth's surface, we have a system 

 of circles to which may be directlj' applied the mechanical principles 

 deduced by Ferrel, Colding, and others. He suggests it as his own 

 belief that the physical reason why we should recur to such a system 

 of central ])rojection consists in the fact that the axes of the cyclones 

 are ordinarily inclined to the earth's surface, as he has in fact satisfied 

 himself by the study of the cyclones that pass over Sicily. {Z. 0. G. M., 

 XIX, p. 454.) 



280. Prof. Elias Loomis, in his nineteenth contribution to meteorology, 

 (American Journal of Science for December, 1883), discusses the baro- 

 metric gradient in great storms, and shows that the effect of friction 

 is greater than as assumed by Ferrel in his formula. {Nature, xxix, p. 

 252.) 



281. In his twentieth contribution (American Journal for July, 1884), 

 Professor Loomis especially discusses the reduction of barometric obser- 

 vations to sea-level ; he concludes that the pressure coefiicient in the 

 hypsometric formula of Laplace is too small. 



282. [As this conclusion is based on the assumption that the tempera- 

 ture of a mass of air below the mountain top is correctly given by tak- 

 ing the mean of the temperatures as ordinarily observed near the ground 

 at top and bottom, which assumption is quite erroneous for the clear 

 nights and days that prevail during high pressures, but more nearly 

 correct for the cloudy weather and high winds that prevail during low 

 pressures and storms, it would seem that systematic errors are hereby 

 introduced that must affect his conclusions ] 



IX. — (a) General storms; (&) Local storms; (c) General wea- 

 ther RELAIIONS. 



283. Dr. W. Koppen has published charts of the frequency and mean 

 paths of barometric minima between the Rocky Mountains and the Ural. 

 His charts are based upon the recent work of Eurojiean meteorologists, 

 especially Hofi'meyer and Hageman, and upon the work of the Signal 

 Office during 1873 to 1879, especially its international bulletin. [His 

 frequency charts are similar to those compiled in 1874 by Abbe, and 

 published by the United States Census Office, and those of Finley re- 

 cently published by the Signal Office, while his charts of mean storm 

 tracks are similar to those coin[>iled by Lieutenant Jackson pnder the 

 special orders of General Myei, in 1875.] Koppen has, however, greatly 

 improved upon i)revions i)ublications of this kind, not only in more 

 careful collation of data, but especially in that for the first time he 

 brought Ameri(;an and European storms together in sufficient number 

 to show the general relations between them. He finds that the move- 



