RECENT SCIENCE. 391 



science is the hope of the world ; that while I yield to none in 

 my love of imagination, of literature, and of all the fine arts, they 

 are as the gracious flowers of the mind-plant whose leaves and 

 roots are the truths of science. True that the living plant is most 

 beautiful when it is in blossom. He who plucks off the flower, 

 while marring the beauty of the plant, destroys the fruit forever. 

 — Abridged from the Journal of the Society of Arts. 



-♦-•*- 



RECENT SCIENCE. 

 Bt peince kropotkin. 



DURING the last thirty years the data of meteorology have 

 been accumulated with a very great rapidity, and the chief 

 desideratum of the moment is, to construct with these data such 

 a general theory of the circulation of the atmosphere as would 

 embody the distribution of heat, pressure, moisture, and winds 

 over the surface of the earth, and represent them as consequences 

 of well-established mechanical laws. The old provisory hypothe- 

 sis of atmospheric circulation, advocated by Hadley in 1735, and 

 further elaborated by Dove in our century, can be held no more, 

 and a new theory has become of absolute necessity. 



We all have learned Dove's theory at school, even though we 

 often found it difficult to understand. The air, greatly heated 

 on or near the equator, rises in the same way as it rises in the 

 summer over a sunburned plain. On reaching the higher strata of 

 the atmosphere it flows toward the poles, but, owing to the speed 

 of rotation which it has acquired in the lower latitudes, it is de- 

 flected — to consider the northern hemisphere only — to the right, 

 and blows in the upper strata as a current from the southwest. 

 To compensate this flow, air rushes on the earth's surface toward 

 the equator, and as it also is deflected from its course by the same 

 inertia of rotation, it appears in the tropics as a trade wind blow- 

 ing from the northeast. However, the upper warm current does 

 not flow all the way to the pole in the upper regions ; it is grad- 

 ually cooled down, and in about the thirtieth degree of latitude it 

 begins to descend to the earth's surface, where it meets with the 

 cold polar current. A struggle between the two winds ensues, and 

 it lasts until they make a temporary peace by blowing side by 

 side, or one above the other, the struggle giving origin to storms 

 and to changes of wind which are fully analyzed in Dove's theory. 

 A rope without end rolling over two pulleys, one of which lies 

 horizontally near the equator, and the other stands upright in 



