DYNAMIC METEOROLOGY. 375 



bodies. Tbe true explanation of Ilagen's results and of tbe production 

 of drafts by wind transverse to the chimney flue is found in the study 

 of the pressure within discontinuous spaces and the vortices attending 

 tbe flow of liquid past any resisting body. The same criticism applies 

 to Ferrel's explanation of the pumping of the barometer, in so far as he 

 implies that friction drags away the air. 



In his sixth chapter Ferrel gives an excellent exposition of harmonic 

 analysis as applied to periodic phenomena, which is followed by the 

 fundamental princi[)les of thermometry, actinometry, hygrometry, ba- 

 rometry, and anemometry. Among the new things, we notice that he 

 introduces here the analytical })ortion of his investigations upon tbe 

 psychrometric formula, the numerical portion of which is published by 

 him in full as an appendix to the annual report of the Chief Signal 

 Officer for 18SG. In regard to the reduction of tbe barometer to sea- 

 level be recommends, on page 398, the use of jnonthly normals for the 

 upper and lower station. In order to diminish the diurnal temperature 

 effect he has since then acceded to the i)resent practice of the Signal 

 Service in the use of mean daily temperatures. 



In 1886, to the great regret of his colleagues, Professor Ferrel an- 

 nounced that, conformably to a long-cherished resolution, be should 

 celebrate his seventieth birthday by resigning official public office and 

 retiring to his homestead in Kansas City, Missouri. The leisure thus 

 secured, we learn, has been used in the preparation of a "Popular 

 Treatise on the Winds," which will be published in 1889 and be doubly 

 welcomed by the student of meteorology. 



(12) kSjjrung. — In 1885 Dr. A. Sprung published his Lebrbuch der Me- 

 teorologie. Shortly afterward he. moved to Berlin, and as instructor in 

 the university and as assistant under Professor Bezold has exerted a 

 strong and good influence on the progress of meteorology. 



His Lebrbuch is by far the best treatise extant on dynamic meteor- 

 ology, and I have included it in this section of theories of atmospheric 

 motion, because Dr. Sprung has devoted two-thirds of his Treatise to the 

 exposition of tbe views that have been worked out by the mathemati- 

 cians whose luimes are already so familiar to my readers. It is scarcely 

 necessary to say that the volume contains nearly all that bad been sat- 

 isfactorily established in dynamic meteorology at that time. Those who 

 have not access to — or time to consult — tbe original memoirs should by 

 all means study this volume. 



Of the other general treatises those that bear especially on storms 

 are: 



(13) Greely. — "American weather," by Gen. A. W. Greely, in which 

 the statistics of American storms are quoted to substantiate the theory 

 of their progress by transportation in the general drift of the atmos- 

 phere. 



(14) Scott — "Elementary meteorology," by R. B. Scott, in which only 

 a small section is devoted to storms. 



