RECENT SCIENCE. 393 



However, the very progress achieved demonstrated the neces- 

 sity of a more thorough knowledge of the too much neglected up- 

 per currents of the atmosphere. In Dove's scheme, the upper 

 equatorial current, after part of it had been sent back to the equa- 

 tor, was entirely abandoned to itself, to make its way as best it 

 could against the opposed polar winds; but the existence of a 

 strong, nearly permanent, and relatively warm upper wind blow- 

 ing toward the east in our latitudes — which was only probable 

 thirty years ago * — became more and more evident, especially 

 since the movements of clouds began to be systematically studied 

 and observatories were erected on high mountains ; and this wind 

 remained unexplained in Dove's theory, while in Maury's scheme 

 of atmospheric circulation, which is still in great vogue in our 

 schools, there was even substituted for it a current in an opposite 

 direction, which does not exist, and which Maury himself could 

 not account for.f An entire revision of the subject was thus ne- 

 cessary, and this revision has been done by the American meteor- 

 ologist Ferrel, in a series of elaborate works which are only now 

 beginning to receive from meteorologists the attention they fully 

 deserve. 



Ferrel's theory is based upon considerations as to the laws of 

 motion of liquids and gases of different densities. If the whole 

 atmosphere were equally heated in all its parts, and at full rest, 

 the air would be disposed in horizontal layers, of greater density 

 at the bottom, and of decreasing density toward the top. Consid- 

 ering some part only of the atmosphere, from pole to equator, and 

 neglecting the curved surface of the earth, we should thus have 

 something analogous to a trough filled with layers of different 

 liquids. If one end of the trough were now warmed, and the 

 other end were cooled, the layers would be horizontal no more. 



* Observations in Siberia — namely, at the graphite works on Mount Alibert, at a height 

 of eight thousand feet (52° north latitude) — were especially conclusive. Alibert's observa- 

 tions, buried in the Russian Trudy of the Siberian expedition, proved the existence of a 

 nearly permanent west and west-northwest wind on the top of the peak, and they showed 

 at the same time that the average yearly temperature on the top of the peak was by some 

 fourteen to eighteen Fahrenheit degrees higher than it otherwise ought to be. When I 

 visited the then abandoned mine in 1864, and saw the peak dominating all surrounding 

 mountains, and could judge of the force of the west wind from the immense works accom- 

 plished to protect the road which was traced on the western side of the peak, I could not 

 refrain from explaining the extraordinary great height of the snow-line in east Siberia by the 

 existence of a relatively warm equatorial current blowing with a great force at a height of 

 from eight to ten thousand feet in the latitude of 52° north. Later on the observations 

 which I brought from the Voznesensk mine (60° north, altitude twenty-six hundred and 

 twenty feet) induced my friend Ferd. Miiller, who calculated those observations, to conclude 

 that in higher latitudes the same current descends still lower to the earth's surface, and still 

 maintains some of its initial warmth. 



f See James Thomson's paper On the Grand Currents of the Atmosphere, in Philosoph- 

 ical Transactions, A. 1892, p. 6Y1. 



