262 = oS. SJ. Stevenson—Laults of Southwest Virginia. 
Pacific oceans ; a high area generally prevails over Kuropasia, 
frequently showing more than one center of maximum pressure, 
and a moderately high area generally prevails over some part of 
North America, but ‘it is not as persistent as the high area over 
Asia. 
The facts stated in this paper clearly show that the movement 
of areas of high pressure depends upon very different causes 
from that of areas of low pressure. Areas of low pressure seem 
to be endowed with a power of locomotion which resides within 
themselves. The heat liberated in the condensation of vapor 
develops a power which draws in the surrounding air, and this 
motion, combined with the movement which results from the 
general system of atmospheric circulation, causes a rapid dis- 
placement of the low center. Areas of high pressure exhibit 
no such power. Their low temperature creates a tendency to 
crowd toward a warmer region; and this tendency is obscurely 
seen in the high areas of HKurope and Asia. It is more dis- 
tinctly seen in the high areas of the United States, probably on 
account of the proximity of a much higher temperature, viz: 
the Gulf of Mexico on the south, and the Atlantic Ocean with 
the Gulf Stream on the east. Aside from this cause, the move- 
ment of areas of high pressure seems to depend entirely upon 
external forces. A neighboring area of low pressure may draw 
off the air from oue side, and thereby cause a displacement of 
the center of maximum pressure; or the high area may be 
reénforced at the top insuch a manner as to cause a rapid move- 
ment of the center of maximum pressure, in a direction and 
with a velocity which are apparently subject to no law. 
Art. XXIX.—The Faults of Southwest Virginia ; by JOHN J. 
STEVENSON, Professor in University of the City of New 
York. 
THE existence of great faults in southwest Virginia was 
made known in 1836 by Professor Wm. B. Rogers, three prin- 
cipal faults being shown on the long cross-section appended to 
his ‘‘Reconnaissanee.”* The existence of the Saltville and 
New Garden faults is asserted in a paper on Thermal Springs 
by the same author and in a long memoir on the structure of 
the Appalachian Chain by Professors W. B. and H. D. Rogers.+ 
At a much later date, Professor J. P. Lesley ran several lines 
across portions of the faulted area on both sides of New River 
* Report of the Geological Reconnaissance of the State of Virginia, 1836. 
+ These papers are contained in the volume of the Transactions of the Associa- 
tion of American Geologists and Naturalists, 1840-42. 
