104 CLIN AS OLOG ¥., 
In connection with our winter temperature, it must be mentioned 
that the Mississippi at St. Louis freezes over about once in four or 
five years, partly, no doubt, in consequence of the heavy ice floating 
down from the North, and then remains closed for one or two or 
even four or six weeks, sometimes passable for the heaviest teams. 
Our river has been known to close as early as the first week in 
December, and, in other-years, to open as late as the last week in 
ebruary, while the running ice may impede or interrupt navigation 
_ between the end of November and the end of February, sometimes 
as low down as the southeast corner of the State; the river is said, 
however, never to freeze over below Cape Girardeau. 
The Missouri River is sometimes closed in the latter part of 
November, and has been known to remain firmly bridged over into 
the first week of March. 
The climate of Missouri is on the whole a dry one, with strong 
evaporation and an atmosphere but rarely overloaded with moisture. 
The average amount of vapor, or rather dissolved water, in the 
atmosphere, the relative humidity, is only 66 (66 per cent. of com- 
plete saturation), 72 in winter, 59 in spring, 66 in summer and 68 
in autumn. Thus, spring proves to have the driest atmosphere, 
and April (56) more than any other month, which, by the way, is 
as agd compatible with the considerable fall of rain in spring. 
enjoy in Missouri an unusual amount of fair weather. Our 
autumnal season is celebrated for it, and also in the other parts of 
the year fair weather and bright sunshine prevails to the great 
benefit of organized life and the well-being of the human family. 
Winter. | Spring. | Summer. | Autumn. oe 
Clear or nearly clear davs | 30 33 40 | 40 143 
Aen clear and day 39 47 48 | 39 173 
b 1 21 etieie 12 49 
Meteorologists have still another method to express the same 
facts, by rating the clear sky as o, and the overcast one as 10, with 
the intermediate grades. After this method, we find the five months 
from November to March rated between 5 and 51%; April, May, 
and October between 4 and 5; June till September between 314 
and 4; and the whole average year at 414 of proportional cloudi- 
ness. 
The average annual rainfall, including the melted snow, in St. 
Louis is 41 inches, but varies considerably in different years ; it 
has been as low as 25 and as high as 68 inches. Our regular 
rainy season extends from the middle of April to the middle of 
July, comprising the latter part of spring and the earlier part of 
mer. This, however, often suffers exceptions, as in our latitude 
the seasons are not so distinctly marked as nearer the tropics. 
RAINFALL, | Winter Spring. | Summer. | Autumn. be song 
Average rainfall in inches | 7 “a “ ; | > 
Highest a6 os By = PH 
MOC iis cncin vip apniindscs sanneukindiinkeuescbeuen ' 2 5 5 3 25 
In the low southeastern part of the State, the annual rainfall is 
at least five inches higher than at St. Louis, while westward and 
northwestward, it diminishes to not more than 30 inches. 
Our summer rains mostly descend with great abundance and in a 
comparatively short time, so that the average 13 inches of summer 
rain fall in 70 hours, distributed over 24 days, while the 7 inches 
of winter rain (and snow) descend in 160 hours and on 22 
days. The days on which it rains vary between 68 and 115 in the 
year, in the average 92. 
Snow is ratherscarce in our climate, and rarely continually covers 
the ground for more than a few days or a week, but it has been 
known to fall about St. Louis as early as October 5, and as late as 
April 16. In some years it amounted, when melted, to 5 14 inches, 
in others to only one-half inch; the average is about 2% inches. 
Our rivers rise—in consequence of the heaviness of our spring 
and summer rains much more than from the thawing of snows in 
the northwestern plains and mountains,—generally between April 
and June, the Mississippi at St. Louis sometimes not more than 
20 or 25 feet, but occasionally (1844) as much as 44 feet, above 
low water mark, while in the fall and winter months they are 
quite low. 
The Oa re pressure Gadicned by the stage of the barom- 
eter) is with us in summer more uniform and regular than on the 
Atlantic coast, while in winter it fluctuates considerably, and often 
‘very rapidly. The average barometrical pressure is highest in 
January, falls till May and then gradually rises again till January ; 
it is most variable from November to March, and least so from 
June to August. 
The barometrical indications perfectly ree tetre with the winds ; 
they are more moderate here in the interior than on the Atlantic 
coast, but winter storms from the West and Northwest are not rare, 
and extend over the whole country, traveling from the Rocky 
Mountains across the Mississippi Valley to the Atlantic coast in 
about two days. During the winter season, westerly winds prevail 
scarcely more than southeasterly ones, while during the warmer 
months, from May to October,‘southeasterly ones largely predom- 
inate over all others. 
Thunderstorms are frequent in spring, (on an average 14,) and 
especially in summer (20), especially from May to July; much 
rarer in autumn (7), and winter (2). In the warmer seasons they 
are sometimes accompanied by short but violent tornadoes, which 
invariably, like most thunderstorms, come from the southwest, and 
sometimes do considerable damage. Violent hail storms have pre- 
vailed in some seasons and some localities, while others have been 
free from their isjurious visitations. 
The native vegetation which covers the surface of our State results 
from the climatological conditions above enumerated, and thus per- 
mits us to judge of and mark these conditions. In the southwestern 
corner of the State, marked on the map as being blessed with the 
warmest temperature and the greatest moisture, we find the cypress 
and the cane in the predominating low grounds, and the Spanish 
oak, mixed with more northern oaks and hickories on the 
slopes. Besides corn and tobacco, cotton is a staple product of 
this district. West and north of this region we find the broad belt 
of timbered lands of the State, which sends its spurs up the river 
valleys. The characteristic trees in the wide river bottoms are, 
the cottonwood and the sycamore, the elm and black walnut, the 
pecan, the hackberry and the honey locust, with very few oaks. The 
smaller river and creek bottoms, and the slopes of their bluffs, are 
the favorite localities for the linden, the mulberry, the black birch, 
the buckeye, the silver maple, while on the fertile hills the sugar 
maple abounds, with several species of hickory. The rolling 
uplands are characterized by numerous oaks, prominent among 
which is the whife, post and black oak, and the different hickories. 
Wheat, corn, hemp and tobacco are the staples of this district, 
distributed according to the fertility of the soil. 
The only pine woods in the State (yellow pine, Pinus mitis,) 
are found where the Silurian formation furnishes a sufficiency of 
silicious material ; they occupy a belt south of the Missouri River, . 
extending in a southwestern direction along the Ozark hills. 
West and northwest of the timbered region spread the great 
prairies, covered with native grasses, interspersed with numerous 
flowering herbs, especially of the aster and sunflower tribes; even 
here some timber is generally found in the valleys along the water 
courses, and sometimes on the ridges. They furnish excellent wheat 
and corn lands. 
