169. If, whenever it becomes necessary to call in the half-crowns, a new coin of the value of two shillings were issued, which should be called by some name implying a unit (a prince, for instance), we should have the tenth part of a sovereign. A few years after, when the public were familiar with this coin, it might be divided into one hundred instead of ninety-six farthings; and it would then consist of twenty-five pence, each of which would be four per cent. less in value than the former penny. The shillings and six-pences being then withdrawn from circulation, their place might be supplied with silver coins each worth five of the new pence, and by others of ten-pence, and of twopence halfpenny; the latter coin, having a distinct name, would be the tenth part of a prince. 170. The various manufactured commodities, and the various property possessed by the inhabitants of a country, all become measured by the standard thus introduced. But it must be observed that the value of gold is itself variable; and that, like all other commodities, its price depends on the extent of the demand compared with that of the supply. 171. As transactions multiply, and the sums to be paid become large, the actual transfer of the precious metals from one individual to another is attended with inconvenience and difficulty, and it is found more convenient to substitute written promises to pay on demand specified quantities of gold. These promises are called bank-notes; and when the person or body issuing them is known to be able to fulfil the pledge, the note will circulate for a long time before it gets into the hands of any person who may wish to make use of the gold it represents. These paper representatives supply the place of a certain quantity of gold; and, being much cheaper, a large portion of the expense of a metallic circulation is saved by their employment. 172. As commercial transactions increase, the transfer of bank-notes is, to a considerable extent, superseded by shorter processes. Banks are established, into which all monies are paid, and out of which all payments are made, through written orders called checks, drawn by those who keep accounts with them. In a large capital, each bank receives, through its numerous customers, checks payable by every other; and if clerks were sent round to receive the amount in banknotes due from each, it would occupy much time, and be attended with some risk and inconvenience.