There are different kinds of fires, depending upon their size, their intensity, and the nature of the country in which they are burning. And there are as many different methods of fighting fire as there are kinds of fires. Some fires, such as grass fires or those burning in the needles and litter in the forest, can be extinguished directly by being smothered or beaten out. For this purpose Rangers sometimes use their saddle blankets, when nothing else is handy, but usually wet gunny sacks, boughs, and tree branches are used. Often, if it is available, sand or dirt is thrown on the fire with a shovel. Surface fires are a little more difficult to extinguish. They are more intense and more swift and consume brush, young growth, and fallen dry trees. These usually cannot be attacked directly, but must be controlled indirectly by the building of a trench or a fire break, or by a system of back firing. Trenches are fire breaks in miniature, usually from one to several feet wide. Fire breaks or fire lines are broad belts from 30 to 50 feet wide, which are cleared of inflammable material, not so much to stop the fire when it reaches this belt as to furnish a safe area from which fire can be fought and, most of all, from which back firing can be started. These lines or belts are usually built along ridges. If a fire starts on the lower slope of a mountain and the wind carries it up the mountain toward the fire line, the only hope of stopping the fire at the top of the ridge at the fire line is to start fires on the top of the ridge, which will burn down the slope and meet the original fire coming up. In rare cases, as, for instance, in the Idaho fires of 1910, the fires get to be so large and swift that all methods of attack prove futile and the only salvation is in natural barriers, such as rivers, or a change of the wind, or rain, to extinguish them. In all fire fighting work, the plan is to surround the fire (if it cannot be beaten or smothered out) by a trench, fire line, or fire break, and to prevent the fire from spreading. In this kind of work, shovels, spades, mattocks, rakes, and hoes are used to move the soil; saws and axes are used to remove fallen trees from the fire line, and in some cases plows, dynamite, and other implements are employed. PROTECTION AGAINST TRESPASS, FOREST INSECTS, EROSION AND OTHER AGENCIES While the protection of the Forest resources from fire is probably the most important phase of forest protection, it is not the only one by any means. The National Forest force also protects the Forest resources from trespass, from insect damages, and from tree diseases. Also water supply for domestic use, for irrigation, water-power, and navigation must be protected, and the public health must be safeguarded against the pollution of the streams emerging from the Forests. It is also the duty of Forest officers, in coöperation with the state authorities, to protect game, fish, and birds from illegal practices.