Naturally some ranges have feed at some seasons of the year and other ranges at other seasons. Some of the National Forests in California extend from an elevation of a few hundred feet in the foothills of the great valleys to an elevation of more than 10,000 feet at the crest of the Sierra Nevada Mountains. The lower foothills afford excellent feed soon after the beginning of the fall rains in November and, due to the very mild winter which this region enjoys, there is excellent feed in February and March. This is known as winter range. The medium high slopes of the mountains have a later growing season and the sheep and cattle reach there about June and stay until August or September. Still higher up the forage matures later and the grazing season extends from August until November. At these elevations the snowbanks usually lie until July and the growing season is very short, for the new snow usually buries the vegetation about the first of November. Thus stockmen have what they call "winter range," "summer range," and "fall range," depending upon what seasons of the year the forage crop can be utilized. The National Forests on the whole contain very little winter range, hence stockmen must move their stock in the fall to private lands at lower elevations either where the climate is considerably warmer or where there is very little snowfall. A large part of the western winter grazing lands are in regions of light snowfall, such as at the lower elevations in Utah, Nevada, Wyoming, and Colorado. Here the stock feeds on dry grass. Stockmen who cannot get winter range lands must feed their stock at ranches. The characteristic habits of sheep and cattle require that they be handled differently on the range. Sheep are herded in bands while cattle are handled in scattered groups. The new and approved method of handling sheep called the "burro system" calls for a burro with the sheep to pack the herder's blankets and provisions. The herder camps where night overtakes him. The herder and his band keep moving over the allotted range from one camp to another until he has covered the whole range. After leaving his last camp he is ready to begin all over again, since the feed near the camp where he began has had two to three weeks' time to grow a new crop. Cattle usually run loose singly or in groups on their allotted range. Usually a range rider is camped on the range to keep the cattle from straying to other ranges. He salts the cattle to keep them on their own range, takes care of cattle that have gotten sick, and takes care of the stock in other ways. _Grazing Districts and Grazing Units._ The Secretary of Agriculture not only has the authority to regulate grazing and prescribe the schedule of grazing fees to be charged but he also regulates the number and class of stock which are allowed to graze on each National Forest annually.