J. D. Dana on the Origin of Mountains. 347 
This difference is caused by the difference in the relative temp- 
eratures of the land and sea in the two seasons, and shows that 
the winds have slightly a monsoon character. uring the 
spring and fall, when the relative temperatures are about the 
same, the winds blow very nearly from the same point, which 
corresponds very nearly with that of the resultant for the whole 
year, which is 3 ) The atmosphere in the course of 
the whole year moves a little more south than north. Dividing 
1920 by 8299, the whole number of observations, we get 0°58 
for the average force in the direction of the resultant. This, by 
the supposed scale used corresponds to a velocity of about eight 
miles per hour, in a direction a little south of east. 
Very respectfully yours, 
Wm. FERREL. 
Professor Benjamin Peirce, Sup’t U. 8. Coast Survey. 
Art. XXXVIII.—On the Origin of Mountains; by James D. 
DANA. 
Some still attribute to this theory makes it desirable that its 
7 Sage poiuts should be stated here with more fulness than 
they were in the notice referred to, and that they receive fur- 
ther consideration. The points in the theory, selected out and 
condensed in the statement from the Introduction to the third 
volume of Professor Hall’s New York Paleontology (where alone 
they have been published), are the following : 
1. The Paleozoic strata of the Appalachian region bear evidence 
that they were mostly of shallow water origin. 
2. Their great thickness, consequently, was attained through a 
slowly progressing subsidence, the axis of which was in the direc- 
tion of the Appalachian chain. 
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