[31]The intermediate employed in actual transactions is, in increasing degree, that form of currency called credit, the lowest order of currency, rather than money itself. Checks and drafts make up a progressively larger share of the circulating medium. The net deposit credits in the national banks in the United States--to say nothing of the other banks--are double the volume of the actual money in the country. And a large share of this actual money is really employed as reserves to support the credit circulation. More than 90 per cent. of the larger sorts of transactions are mediated through the use of deposit credit, and probably more than one-half of the remaining transactions are similarly effected. Thus the study of banking is essential to any understanding of monetary problems.... [32]For a bank, as well as for any other considerable establishment, it is requisite that a capital should be provided at the outset. There can be no constant proportion between the amount of this capital and the extent of the business which may be built up by its means. We can only say that, other things being equal, the larger the business that can be carried on with safety with a given capital, the larger will be the field from which profits can be earned, and the higher the proportion which the profits will bear to the original investment; but the point at which the extension of the business passes the line of safety, must be determined by the circumstances of the particular bank, by the kind of business carried on by those dealing with it, and by the condition of the community in which it is established. The attempt has sometimes been made to limit by law for incorporated banks the proportion of transactions for a given amount of capital, but no such provision has any foundation except a conjectured average, too rough to be of service in any individual case. In this respect, as in so many others, the judgment of the persons most interested, acting under the law of self-preservation, is far more trustworthy than any legislative decision.