132 
METEOROLOGY OF THE FIELD EXPLORED. 
visit Fort Benton, and the Blackfeet Indians go to the valley only to steal horses. Victor, the 
Flathead chief, assured me that his people always recrossed the mountains in December or 
January, generally between Christmas and New Year—men, women, and children—with their 
horses laden with meat and buffalo robes. It was only in a winter of extraordinary severity, 
and at rare intervals, that they could not cross in January and February. I also learned that the 
Washington Territory Indians went to the hunt in October and November, and returned in 
February and March. This information has since been confirmed by myself and the gentlemen 
of my party meeting many hundreds of these Indians on their way to the plains, and ascertaining 
from them and the fathers of the mission their customs in this respect. 
In order to give as wide a range as possible to the general field of exploration, and to accu¬ 
mulate information on this interesting question, Mr. Tinkham was sent back to Fort Benton with 
orders to return by a more southern trail to the St. Mary’s valley, and thence to take the south¬ 
ern Nez Perces trail to Wallah-Wallah, and thence by the military road over the Cascades to 
Nisqually. This last order was modified, and he was directed to cross the Cascades by the 
Snoqualme Pass. 
Expresses were also sent from the Columbia, by Clark’s fork, to the St. Mary’s valley, 
through the winter, and the condition of the snows ascertained during December, January, 
and February. 
The results may be summed up as follows: In the Rocky mountains the greatest average 
depth of snow found by Lieutenant Mullan, from the 28th of November to the 10th of January, 
was only twelve inches, and that only for a short distance over the divide. On the divide from 
the Jefferson fork to Snake river the snow, though only twelve inches deep, was occasionally 
drifted from two to three feet deep. 
In this period he made an exploration to Fort Hall, going and returning on different routes, 
crossing the mountains lour several times, and making an aggregate distance of more than seven 
hundred miles. The mountain region thus crossed was from the forks of the Missouri to the Hell 
Gate river. On the divide leading to the Hell Gate river, there was but two inches of snow 
on the 31st of December. I will call attention to the circumstance that, on the divide from the 
Three Forks to the Salmon river, Lieutenant Mullan’s guide found but three feet of snow in 
the winter of 1852-53—a season remarkable for the great quantity of snow which fell—and 
that he crossed it in the winter with his horses. 
The grass, except from the Snake River divide to Fort Hall, was rich and luxuriant in the 
valleys. The w r eather was as cold as in many parts of the New England States; the ther¬ 
mometer falling in some cases to 2S° below zero. 
On the 27th of January Lieutenant Mullan writes me that Victor, with the Indians of his own 
and other tribes, were crossing the mountains from the buffalo plains. 
In March Lieutenant Mullan went to Fort Benton by the southern and Little Blackfoot, and 
returned by the northern Little Blackfoot Pass, finding but ten inches on the first pass and no 
snow on the second pass. 
Lieutenant Grover, after his survey of the upper Missouri, remained at Fort Benton through the 
month of December, during which month the Missouri had been obstructed only a day or two 
with ice. He left Fort Benton on the second day of January, no snow having fallen till the pre¬ 
vious evening, and crossing the divide by Cadotte’s Pass he found but one foot of snow on the 
divide and on the Blackfoot trail; thence to Wallah-Wallah, which he reached on the fourth day of 
March, he found little or no snow in the valleys and on the prairies till he reached Thompson’s 
prairie, on Clark’s fork. From this point his course was through a densely wooded country, 
and the snow gradually increased in depth till at the distance of fifty miles it reached the depth 
of two feet, and remained about this depth till within a few miles of the Pend d’Oreille lake, 
where it began to decrease, and in the immediate vicinity of the lake was only one foot deep. On 
the shores of the lake the snow continued to decrease, and occasionally a fine field of grass was 
