of labor-time. Since labor-time constitutes the substance and the intrinsic measure of values, these names would then actually represent definite proportions of value. In other words, labor-time is maintained to be the true unit of measure of money. With this we leave the Birmingham school, but should add in passing that the doctrine of the ideal measure of money acquired new importance in the controversy over the question of the convertibility or non-convertibility of bank notes. If paper receives its name from gold or silver, then the convertibility of a note or its exchangeability for gold or silver remains an economic law, no matter what the civil law may be. Thus a Prussian paper thaler, although legally inconvertible, would immediately depreciate if it were worth less than a silver thaler in ordinary trade, i. e., if it were not practically convertible. The consistent advocates of inconvertible paper money in England, therefore, sought refuge in the ideal measure of money. If the reckoning names of money, £, s., etc., are names of certain quantities of atoms of value, of which a commodity absorbs or loses now more, now less in exchange for other commodities, then an English £5 note, e. g., is just as independent of its relation to gold as of that to iron and cotton. Since its title would no more imply its theoretical equality with a certain quantity of gold or any other commodity, the demand for its convertibility, i. e., for its practical equality with a definite quantity of a specified thing would be excluded by the very conception of the note.
The theory of labor-time as the direct measure of money was first systematically developed by JOHN
