/\ Waldo— Contributions to Dynamical Meteorology. 283 



earth may become in the formation of the atmospheric motions. 

 The Erictional influence of rough ground is more or less pro 

 Qoonced according to the peculiarities of the air currents; 

 whether they are ascending, descending, or horizontal. The 

 author Investigates this action in Borne genera] types of circula 

 tion. He contrasts the peculiarities o\' two continental atmos- 

 pheric depressions ; in the one an upward current preponder- 

 ates, while in the other a downward current is the ruling one. 

 In the first ease, the one in which the depression has a warm 

 center and an upward current, the relatively quiet air near the 

 Burface of the earth carries with it no great force and iii fact 

 has a retarding influence on the hpper currents; and in the 



-lid rase, where the depression has a cold center and there 

 i- a downward current, the feeding current easily acquires a 

 it velocity. These two conditions cause very different re- 

 >nlts, and the author brings out these differences. Jt must be 

 remembered that Ferrel first pointed out that at the poles 

 there is a depression of the second class, and that the great 

 movements of the masses of air to the eastward in middle 

 latitudes are hut a part of this great system. The author, 

 however, thinks that Ferrel has not sufficiently considered the 

 effects of friction, and he modilies Ferrel's numerical results 



much that in some cases he reverses the latter. Treating of 

 the mixing of air masses having different velocities the author 

 does n«»t agree with the results obtained by Siemens in No. 1. 

 He thinks that the transmission of force does not take place 

 according to the law of preservation of living force, when we 

 wish to compute the resulting velocity, but it follows the law 

 of inelastic impacts. This he proceeds to illustrate by a short 

 computation. 



. A — This article was called out by Moller's strictures in 

 No. 2 against Siemens's methods in No. 1. Siemens thinks 

 that Moller's conceptions are wrong as to the waste of force 

 by friction, and assumes that the layers of air close to the 

 earth are in relative rest, and the thickness of this layer 

 depends on the roughness of the surface; while the upper air 

 layers are practically free from these frictional influences. As 



irds the mixing of currents having different velocities, 

 Siemens shows that his assumption concerning this question 

 does not affect his general results; and as for Moller's use of 

 the theory of inelastic impacts, he merely remarks that the 

 necessities of the question do not call for its consideration. 

 Siemens regards the coincidence between his and Ferrel's views 

 of the atmospheric motion in the neighborhood of the 35th 

 parallel as accidental, as Ferrel has not considered the inertia or 

 the friction, while he (Siemens) has taken into consideration 

 by computation the final condition of equilibrium. Siemens 



