GEOLOGICAL SUEVEY OF THE TEERITOEIES. 



253 



angle, runs northwest diagonally through the district ; the Bitter-Eoot, 

 rising in the southwest angle, runs north near the western border ; and 

 the JBig Blackfoot, rising in the Rocky Mountains, to the east, runs west- 

 ward along the northern border. All that portion lying south of Hell 

 Gate River is traversed north and south by a series of somewhat paral- 

 lel ridges, separated by intervening valleys of greater or less width, each 

 drained by one leading stream, which runs north to the great diagonal 

 channel. The most important of these valleys, in an agricultural point 

 of view, are those watered by the Deer Lodge and Bitter-Root Rivers. 



Deer Lodge Valley is about forty miles long, with an average width of 

 twelve miles that can be irrigated and cultivated. The surface is a broad , 

 level bottom, occasionally flanked by terraces, which, at most points, can 

 be reached by irrigating-ditches afew miles in length, as the descent of the 

 stream is quite rapid. The soil is good, being covered in a natural state 

 by a heavy growth of rich and nutritious grasses, and when properly 

 irrigated and cultivated will yield abundant crops of such things as are 

 adapted to the climate. Not only is it supplied with water by the cen- 

 tral stream, which traverses the entire length of the valley, but there 

 are quite a number of smaller rivulets which flow in from the mountains 

 to the right and left. Below Deer Lodge City the hills close in upon the 

 valley, leaving a narrow, fertile bottom, which does not average more 

 than three-fourths of a mile in width. 



As the elevation, which is but little under 5,000 feet, is greater than 

 that of the valleys lying west of it, and most of those east of the range^ 

 its climate is less favorable for agriculture than some other portions of 

 the Territory. Mr, Granville Stuart, of Deer Lodge City, who is a very 

 careful observer, gives the following as the monthly means of the tem- 

 perature for 1868 and 1869: 



This gives the yearly mean of the temperature for two years 40.7^ 

 and the mean of the seasons as follows : spring, 41.6 ; summer, 69.7 j 

 autumn, 43.1 ; winter, 19.9. Althougb 1868 gives a higher mean than 

 1869, yet January of the former appears to have been unusually cold. 

 This list also brings out the fact that the seasons are very variable^ 

 whicli is really the greatest climatic impediment to agriculture in these 

 mountain regions. For example, there is a difference of 21,9 between 

 the means of January for the two years ; of 11.4 in March, that of 1868 

 being in excess, while in May, 1869, is ll.l in excess, this holding good 

 through the summer months ; but in October that of 1869 falls 24^ 

 below that of 1868; whereas the means of the next month show 1868 

 6.1 below 18B9. Such variations show that the mean annual depression 

 of the thermometer is caused not so much by a uniformly rigorous 

 climate, as by sudden cold spells, which, though continuing but a short 

 time, serve to bring down the means. For example, we may feel confi- 

 dent from this table that some time during the month of October, 1869^ 

 there was a sudden change and a cold spell. It must be remembered 

 that this record, which shows a somewhat rigorous climate, was made 

 where the elevation is 4,768 feet above the level of the sea, and is con- 



