SHORT MEMOIRS ON METEOROLOGICAL SUBJECTS. 447 



I. 



SOME EEMAEKS CONCERNING THE NATURE OF CURRENTS 



OF AIR. 



By a. Coldixg. 



[Translated by CleTeIan<l Abbo anJ H. L. Thomas, from the Oversigt over det K. Danske Viden- 

 skabernes Selskabs .... Aaret 1871, page 89, with occasional reference to Hann in Zoitschrift Oeat. 

 ilet. Ges., vol. x.] 



These remarks are based mainly upon the results of certain investi- 

 gations into the movement of water in currents* which I had the honor 



* [Note by the Teansiator, February, 1B78.— The article G of the present col- 

 lection gives some idea of the results of Ferrel's dynamical theory of the winds and 

 currents on a rotating globe, but as the writings of Colding, Peslin, and others have 

 considerable merit as being the best that can be done with the purely kinematic theory, 

 the translator takes pleasure in aleo presenting their memoirs to American students, 

 and as a corrective to these would refer to Mr. Ferrel's criticisms in " Nature " for 1871 

 aud 1872, as well as his memoirs of 185G, 1859, and 1877. 



The general problem of movement on the earth's surface was treated of in an imper- 

 fect way by numerous authors from Hadley and Newton to Laplace and Poisson. The 

 latter in 1837, in his memoir on the movements of projectiles, among other things, 

 mentioned the deviation of the projectile to the right produced by the rotation of the 

 earth, but appears to have overlooked its importance as a dynamic law and to have 

 derived it from geometrical or kinetic principles. 



In 1832, Professor Johnson published, in the American Journal of Science, a memoir 

 upon his rotascope. In 1851, Foucault presented to the Academy of Sciences of Paris 

 his famous pendulum experiments, and subsequently his gyroscope. Both these autliors 

 explained the phenomena in question on purely kinetic principles, or on the presumed 

 law that a rotating body tends to preserve its axis of rotation. Hereupon followed a 

 long discussion in the Paris Academy (fully reported in the Comptes Rendus, tome 

 xxxii-li, 1851-1860), in which many eminent men took part. Poinsot and others would 

 explain the phenomena by the purely geometrical laws of the composition of rotations ; 

 but the dynamics of the problem were exposed by Birnet, C. R., 1851, xxxii, pp. 157 and 

 197; by Babinet, C. R., 1859, xlix, pp. 638, 686, and 769; Delaunay, C. R., 1859, xli, p. 

 688; and Poncelet, C. R., 1860, li, pp. 467 and 511. 



Meanwhile the gyroscope also was exciting renewed attention in the United States, 

 and an original and satisfactory investigation of its phenomena (the first that I know 

 of based on correct general dynamical principles) was published by Ferrel in 1856 in 

 the "Nashville Journal of Medicine and Surgery," vol. xi (see also in "Gould's Astron. 

 Jour." and in "Runkle's Math. Monthly"). Of other investigations I note only one 

 (kinetic and not dynamic), by General J. G. Barnard, in Am. Jour. Sci. (several papers 

 from 1855 to 1859), see also his "Problems of Rotary Motion" in the Smithsonian Con- 

 tributions, xix, and his article "Gyroscope" (where fundamental principles are intro- 

 duced) in Johnson's Cyclopasdia, N. Y., 1877 ; also, Snell on the "Rotascope" in Ann. 

 Rep. Secretary of the Smithsonian Inst., 1855. 



Mr. Ferrel's paper on the gyroscope was immediately preceded by his first essay 

 (1S56) on the winds and oceanic currents, an elementary paper published in the same 

 volume of the Nashville Journal. His more elaborate mathematical memoir was fin- 

 ished in 1853, and published during 1859 and 1860, as " The Motions of Fluids and Solids 

 Relative to the Earth's Surface," in the Mathematical Monthly; separate copies, with 

 a few additional words, were struck off in 1860. This memoir of 72 pages has been 

 further elaborated into " Meteorological Researches, Part I," publi.^hed by the United 



