There is, first of all, the difficulty which we may term personal. A man now accepts trade as a matter of course. He devotes himself to some special line of production, the growing of wheat or the making of shoes, feeling sure that he can exchange his surplus for whatever else he wants, and making his exchanges without hesitation. An uncivilized man, however, is accustomed to satisfy his wants in only two ways, by his own labor in production or by robbing another man. He is suspicious of any offer to exchange wares, and is unwilling to apply himself to any special line of production that would make him dependent on trade. The ignorance and suspicions of men were in early times the greatest hindrances to the rise of commerce, as they are still in backward portions of the world; it has required generations of experience to teach men wants for things which they did not themselves produce, and to teach them to satisfy these wants by exchange. Commerce took on definite proportions and became of considerable importance only when a special class of traders and merchants arose, who made it their business to study wants, to inspire new ones, and to provide the means of satisfying them. =3. (2) Physical obstacles.=—Another difficulty in the pursuit of commerce, which we may term physical, appears in the exchange of articles which are produced at some distance from each other, so that they need to be transported by land or sea. A farmer who sets out for the city with a load of grain will have to count carefully the cost of getting it to market. Assume that he feeds himself and his horses from his wagon-load; evidently, if the road is long, or so bad that progress is slow and many horses are necessary, he may find all the wheat consumed on the journey before he has secured a purchaser. In this aspect the facilities for transportation, whether by land or water, by pack-animal, cart, canal boat or steamer, are of great importance. It has been estimated that a human burden bearer would require more than a day and a half to move a ton of goods a mile; a strong pack-horse can carry three hundredweight a considerable number of miles in a day; while on first-rate level roads a horse can drag a ton even further. Another factor in this question is the character of the ware. A farmer who could not afford to bring wheat to market might still find it profitable to bring butter, which has much greater value in the same bulk, so that the profits on a wagon-load might pay the expenses of the journey. Gold can be exported from the interior of Alaska under difficulties which would make the transportation of any other product impossible.