8 Geology, &c. of the country west of the Rocky Mountamns. 
derlaid by very friable sandstone, and clothed with a very heavy 
growth of timber. 
The Wallamette, (Multnomah,) is of much less extent than 
has been supposed, not being more than two: hundred miles in 
length. Along its spreading branches above its falls, to which the 
tide flows, about twenty miles from its mouth, extends a very beau- 
tiful valley, of interspersed prairie and woodland. West of this val- 
ley, are the mountains extending along the coast, and on the east the 
range stretches south from the cascades, in which rise Mounts Hood, 
Ida, and others; also on the north of the Columbia are St. Helen, 
and other mountains still further north, which are of a conical form, 
and of such height as always to be clothed with snow, while it sel- 
dom falls in the plains. ‘These extinct volcanos, although probably 
not so high as the Rocky mountains, appear covered with snow at a 
less elevation, proving the truth of the suggestion, that constant con- 
gelation descends much lower on detached mountains, than on eleva- 
ted plas i the same latitude. 
By the following meteorological observations, it will be perceived, 
that the winters on the Columbia are remarkably mild, there being 
no snow, and the river being obstructed by ice but a few days during 
the first part of January. Grass remained in sufficient perfection to 
afford good feed; and garden vegetables, like turnips and carrots, 
were not destroyed, but no trees blossomed till March, except wil- 
lows, alders, &c. Often a frost in clear nights, from Oct. till May. 
The difference in temperature in winter, between the eastern and 
western sides of our continent is indeed very great; even more 
striking than between the Atlantic side and Europe. It now appears 
a settled fact, that the eastern sides of the two great continents are 
much colder in the same latitude than the western, and need we 
seek further for the cause, than the prevalence of westerly winds in 
the northern temperate zone, bringing the tempered air of the oceans 
over. the land; and in winter, the wind from the same direction, bear- 
ing on the accumulating cold to the eastern sides of the continents. 
A return from the Columbia river by water around Cape Horn, 
touching at the Sandwich and Society Islands gave some opportunity 
to observe the winds and other phenomena; but having said much 
already, only one thing more shall be added. During three weeks 
stay at Tahite, the tide was observed to rise about one foot, and al- 
ways highest at twelve o’clock, noon and midnight, and I was infor- 
med that this is always the case. 
