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36 Proceedings of the American Philosophical Society. 
discussion of its peculiarities, that it was not—the progress of the baro- 
metric minimum in Europe being from north to south, inclining a little to 
the west. 
The author next proceeds to generalize the deductions in regard to the 
circumstances of this storm, and to apply them as tests to the different 
theories of wind, rain, &c. 
He first endeavors to show how far registered observations of the wind 
may be influenced by localities, and their accuracy affected by the mode 
of observing, and the transcribing of the registers; and concludes that it 
is indispensable to regard the average of directions at near+stations, and 
not those at individual ones, and gives some examples of discrepancies at 
places near each other in support of this opinion. The anomalies pre- 
sented by the stations in the State of New York are very curious. 
The causes assigned by theory for the production of winds are next 
enumerated and discussed. Recurring to the observations, the author 
traces a connection between the direction of the surface wind on the 18th 
and 19th of December, and a maximum of the barometer existing on a 
line nearly north and south, moving eastwardly, and passing on the morn- 
ing of the 20th of December nearly through the eastern extremity of the 
State of Maine. At this period a minimum of the barometer existed 
nearly on the line of the river Mississippi, and the winds blew towards 
this line. This minimum is traced in its motion eastward ; and in con- 
nection with it, the change of wind from the easterly to the westerly 
vailed at nearly all the stations. The direction and approximate force of. 
the wind on the morning of the 2st, are represented upon a map of the 
United States, accompanying the memoir. From an examination of a 
phenomenon of the wind, Prof. Loomis concludes that the southeasterly 
current rose, so that the northwesterly wind thus became the lowermost 
current; and subsequently, from an examination of the phenomenon of 
the rain, snow and hail, that the rising current was, in part at least, de- 
flected back upon itself. The immediate cause of the southeasterly wind 
is traced to the existence of a minimum of pressure at some point north 
of the United States. 
The author next examines the various causes which have been, or may 
be, in his opinion, assigned as producing rain, and infers that the most 
common cause of rain, in these latitudes, is the sudden lifting up of 
warm air into regions about the earth’s surface, by its displacement by . 
— 
a cold current originally above it, and from an opposite direction ; and a 
that such was the actual cause of the rain in question, a warm current 
from the south having been displaced, and caused to rise to a considera 
ble elevation by a cold current from the west. The mixture of the warm 
d cold air is inadequate, in the author’s opinion, to account for the phe- 
nomena. 
