Since improvements in method so constantly lessen the normal value of products, Mr. Carey made the effort to measure value by “cost of reproduction,” meaning, I suppose, that any article produced at any time and place is likely to bring in any market a price equal to the cost of similar articles produced under the most improved methods anywhere used in the present. This, of course, does not apply to articles not desired in the present, because deteriorated or out of fashion or less useful than some new device for a similar use, but only to those articles of full utility in having all the qualities needed to meet the desire of purchasers. Even a diamond like the famous “Kohinoor” would have its almost priceless value reduced to the cost of securing similar jewels equally desirable if a process of crystallizing carbon were suddenly discovered. It is easy to see, then, that cost measures value only so far as it is directly connected with the available supply in any market. Under ordinary circumstances the supply cannot be increased unless the cost is met, but the rule is modified by any peculiarity of season, or conditions of trade, or production by cheaper methods or cheaper labor, or by the changing wants of a community. The application of all these influences may be studied under the so-called law of supply and demand. _Supply and demand; markets._—The law of supply and demand is only a statement of the general fact that market value tends to increase with increase of demand and to decrease as the supply to meet the demand increases. It must be understood that a market means a particular spot where buyers and sellers of any article of commerce meet at a particular time. The supply is the amount offered for sale at a given price. The demand is the amount buyers will purchase at the same price.