but when indoors, the supply may be limited, and they will spend money to have ventilators and air-pipes built to supply them with fresh air. Or take the contrary case: The supply of some commodity, say flour, falls very short. Evidently less flour must be used by the world than was used in the years of a more plentiful wheat harvest. But no one will wish to be the one to go without, and most people will pay a little more rather than do so. Therefore the price rises. The competition which we have chiefly considered is the rivalry which exists between the men who supply the same sort of goods; but there is a rivalry among buyers as well. Speaking generally, every buyer is trying to purchase for as little as possible, and every seller is trying to dispose of his goods or services to the world for as much as possible, which each has a perfect right to do. We have already seen that prices vary with the relative proportion between supply and demand, rising as demand rises or supply fails, and falling as supply increases or demand falls off. But to complete the wonderful perfection of the mechanism, the reciprocal relation is introduced, so that supply and demand vary with price. If the price rises, fewer people can afford to buy and more will be anxious to sell; while if the price falls, more people will wish to buy and fewer people will be willing to sell. We can now easily see why some men are able to take out from the world's common stock of product so large an amount, while most men can take but a meagre allowance. By the law of supply and demand the price is far higher for the service which one man renders to the world than another. Let us take the operation of a large machine shop, for instance. Only one superintendent is needed, and he should be a man who has devoted much time to mastering all the details of the business, and is experienced and competent to so govern the work that a large product will be turned out at a small expense. There is a demand in the country, let us say, for 5,000 such men; but out of the 5,000 who are filling such places, there are perhaps 50 who seem almost faultless in their skill and industry, there are 500 who are with one or two exceptional faults, almost equally efficient, there are 3,000 who are fairly good men, and the rest may be classed as those who hold their positions because better men for the place cannot be had. So with the skilled machinists, the relation of supply and demand is such that the price of their labor is kept up to perhaps $4.00 per day. But of common laborers the supply is so related to demand that the price of their work is very low. Thus the three classes take very unequal amounts from the common stock. The superintendent, perhaps, is able to take five thousand dollars' worth of goods each year. The skilled workman can spend perhaps one thousand five hundred dollars, while the laborer can spend but five or six hundred dollars. Thus the men who secure the greatest amount of