130 METEOROLOGY OF THE FIELD EXPLORED. 
teristic change on the base-line of the survey, and at important points off the line, to gain the 
contour of the country. Each engineer party was provided with its barometer, and careful com- 
parisons were made at night. Occasionally the results were tested by the usual levelling instru- 
ment. Fixed stations were established at Fort Benton, Fort Union, and Cantonment Stevens in 
the St. Mary’s valley, at Vancouver, and at Olympia. Observations were also made for compar- 
ison at Fort Snelling and St. Louis. The final discussions will be made by the officers of the 
Smithsonian Institution, and in connexion with the large body of observations made in all parts 
of the country under their direction. 
30.00 is assumed as the altitude of the mercurial column at the level of the sea for the work 
of the portion east of the Cascades; and a fraction over thirty inches, the result of five months’ 
observation at Vancouver, for the altitude at that place. It is believed the results given in the 
profiles will be found sufficiently near the truth, in the final discussion, to be relied on in the pre- 
liminary computation. 
Much attention has been given to ascertain the circumstances of the snows and freshets of the 
whole country passed over, both by inquiries from all reliable sources and from actual] observation 
by winter parties. Iam able to give conclusive reasons to show that no obstructions whatever 
need be apprehended from snow at any point of the route. From the plateau of the Bois de Sioux 
and the Red river of the North to Lake Superior, two feet is a large quantity of snow, though 
winters have been known when the snow was considerably deeper. The winters are dry, the 
weather clear and bracing, with little or no wind. The mercury, though occasionally it falls to 
a very low point, is seldom below zero. The coldest day of the winter of 1852-53, February 8, 
the mercury fell to 25° below zero, and the winters are from four to four and a half months long. 
Frosts seldom occur before October. The fall climate is remarkably fine. 
The Hon. H. M. Rice, the delegate from Minnesota, has often travelled in winter from St. Paul 
to Crow Wing, a distance of one hundred and fifty miles, with a single horse and sled and without 
a track, and has never found snow deep enough to impede his progress. From Crow Wing 
he has gone to the waters of Hudson’s bay on foot, without snow-shoes. During one winter he 
travelled through that region, finding the snow seldom over nine, and never over eighteen inches 
deep. For several years he had trading-posts extending from Lake Superior to the Red river of 
the North, from 46° to 49° north latitude, and never found the snow too deep to prevent supplies 
from being transported from one part to another with horses. One winter, north of Crow Wing, 
in latitude 47°, he kept sixty head of horses and cattle without feed of any kind, except what 
they could procure themselves under the snow. Voyageurs travel all winter from Lake Superior 
to the Missouri with horses and sleds, having to make their own roads; and yet, with heavy loads, 
are not deterred by snows. Lumbermen. in great numbers, winter in the pine regions of Min- 
nesota with their teams; and the snow is never too deep to prosecute their labor. Occasional 
winters the snow is not over six inches deep. The average close of navigation of the upper Mis- 
sissippi for the last five years is November 26, and the average first spring arrival April 8. 
The Hon. H. H. Sibley, the last delegate from Minnesota, also a most experienced voya- 
geur, states that the snow seldom exceeds fourteen or fifteen inches, and he has known two or 
three winters in succession when there was not snow enough for tolerable sleighing. 
Alexander Culbertson, Esq., the great voyageur and fur-trader of the upper Missouri, and who 
for the last twenty years has made frequent trips by land from St. Louis to Fort Benton, has 
never found the snow drifted enough to interfere with travelling. The average depth of snow is 
twelve inches, and frequently the snow does not exceed six inches. 
The letter of Mr. Rice and extracts from those of Mr. Sibley and Mr. Culbertson are ap- 
pended, for a more full view of the winter climate of the region. 
At St. Paul, the coldest days of six winters are as follows: 
184546 2 cco outer Seay o EUs emia crectecomist ke nee acts) disis (cia 2 ee below zero 18° 
1846-"47 ..... Biale.e athute Gee Rhino Seateiae Sake war eiteitta pee attinateia. «asi ioe a Ke 27 
