Consider that the reindeer feeds upon one thing alone, the moss that is named after him, and that while this moss is very widely distributed indeed, throughout Alaska, it is not found at all in the river valleys or the forests, but only upon the treeless hills at considerable elevation. Now the rivers are the highways. It is on their frozen surface, or on "portage" trails through the woods, that the greater part of all travelling is done and, in particular, that established routes of regular communication are maintained. To leave the trail after a day's journey, to wander miles into the hills, to herd the deer while they browse from slope to slope, digging the snow away in search of their provender, is wholly incompatible with any sustained or regular travel. The reindeer is a timid and almost defenceless creature. Wolves and lynxes prey upon him. One lynx is thought to have killed upward of twenty head in one season out of the herd that was stationed at Tanana, leaping upon the backs of the creatures, cutting their throats, sucking their blood, and riding them until they dropped and died. A few dogs will soon work havoc in a herd. So the reindeer must be constantly protected and at the same time must have range over a considerable scope of country. The care of reindeer is a business in itself, not a mere detail of the business of transportation or travel. [Sidenote: DOG FOOD] On the other hand, the dog's ration for many days is carried on the sled he hauls. There is a definite limit to it, of course, and knowledge of this limit made every experienced dog driver incredulous, from the first, of Doctor Cook's claim to have travelled some eleven hundred miles, from Etah to the North Pole and back, with a team of dogs hauling their own food. It is possible, however, on fair trails, with rigid economy, to travel five hundred miles and haul dog food and man food and the other indispensables of a long journey; and that is twice as far as it is ever necessary to travel in the interior of Alaska without reaching a supply point, the northern slope to the Arctic Ocean excepted.