042 gCIENTIl^^IC RECORD FOR 18S4. 



the depressions results ]iartly from renewed formation, partly from pro- 

 gression; both methods of movement can act in conjunction or in opjm- * 

 sition. In reference to the movement of progression it can be analyzed 

 into three causes : influence of the distribution of atmospheric pressure; 

 influence of the mean distribution of temperature; influence of the 

 earth's rotation. The first influence is treated of by Dr. Koppeu (Z. O. 

 G. M., February, 1880), who shows that the presence of a maximum 

 pressure increases the lower winds and thereby increases the rapidity 

 of movement of the depression. But Moller has also shown that the 

 upper winds carry the depressions with them, so that the progressive 

 movement of a dei)ression is to be considered as a consequence of the 

 movement of a thin layer of warm air and of the movement of a space 

 of rarefied air due to the vis-viva of the forces in action. The third 

 cause of movement, namely, the rotation of the earth, in all latitudes, 

 causes a movement from east to west and also towards the nearest 

 terrestrial pole. In this way he explains the western movements in the 

 torrid zone, where he says this effect of the earih's rotation is at a 

 maximum, while the other causes become efficacious in the middle and 

 higher latitudes. [Moller's poleward tendency seems to be the same as 

 that first pointed out by Ferrel in 1857, but to which w^e believe the lat- 

 ter now attaches less importance. The poleward tendency for the lower 

 winds is balanced by the equatorial tendency due to the higher winds.] 

 As regaids the second cause, namely, the distribution"bf temperature 

 on the earth, this is principally controlled by the sun's heat ; and intro- 

 ducing the algebraic expression for this he shows that the combined 

 influence of heat and rotation is to produce a motion towards the west 

 within 30° of the equator, but toward the east, in more northern lati- 

 tudes, up to a certain limit in the polar circle. The rather complicated 

 formula given by him can be put in tabular form in such a way as to be 

 conveniently used in a strictly scientific estimation of the most proba 

 ble path that will be pursued by any depression. 



287. [It is important that Moller's formulae be applied to the study 

 of the storms of the United States for the purpose of telling more ex- 

 actly the value of the considerations that he has given. It cannot be 

 doubted but that other more important physical laws, such as the con- 

 densation of moisture, the heating of Ihe upper layer of clouds, the 

 relation of continents, oceans, mountain ranges, plateaus, and lowlands 

 have also so large an influence thai the questions of inertia and temper- 

 ature of the moving atmosphere have only a partial if not in fact a 

 subsidiary interest.] {Z. 0. G. M., xix, p. 274.) 



288. R. H. Scott has discussed the question of the reality of the ex- 

 istence of so-called equinoctial storms in the British Islands. To this 

 end he has examined statistics since April, 1870. It is evident from the 

 tables he gives that they simply confirm the results of studies by Dove, 

 Loomis, and others, namely, that no one day of the year is especially 

 Btormy, although the maximum number of storms in England increases 



