[10] In 1862 Mr. Eckfelt, then principal assayer at the mint in Philadelphia, communicated to the American Philosophical Society the result of some exceedingly curious examinations demonstrating the very wide distribution of gold. The city of Philadelphia, he stated, was underlaid by a bed of clay having an area of about ten square miles, with an average depth of about fifteen feet. Specimens of this clay--all natural deposits--taken from such localities as might furnish a fair assay of the whole--the cellar of the market on Market Street, near Eleventh, and from a brick-yard in the suburbs of the city--all yielded, on careful analysis, small amounts of gold; the average amount indicated being seven-tenths of a grain--or about three cents' worth--of gold for every cubit foot of clay. Assuming these data to be correct, the value of the gold, according to Mr. Eckfelt, which lies securely buried underneath the streets and houses of Philadelphia must therefore be equivalent to $128,000,000; or if we include all the clay contained in the corporate limits, the amount of gold contained in it must be equal to all that has yet been obtained from California and Australia. "It is also apparent," says Mr. Eckfelt, "that every time a cart-load of clay is hauled out of a cellar in Philadelphia, enough gold goes with it to pay for the carting; and if the bricks which front our houses could have brought to their surface, in the form of gold-leaf, the amount of gold which they contain, we should have the glittering show of two square inches on every brick." [11] On the Rhine, near Strasburg, a good able-bodied laborer can earn on an average one franc seventy-five centimes per day, washing gold from the sands of the river; but, as under most circumstances he can earn ten sous more by working in the fields on the banks of the river, and without so much risk of getting rheumatism, gold-washing on the Rhine is not often adopted as a regular employment. [12] "And when the substitution is made" (of a silver for a paper fractional currency), "what will be the consequence? The metal currency will have to be considerably debased, or else every old woman in the country will fill her stockings with it and bury it. It will be hoarded, sir; hoarded to the extent of removing millions from the currency of the country." The general paused, glared at a village wrapped in rain, by which we were rattling, chewed his cigar vigorously, and lapsed into silence.--A Newspaper Reporter's Interview with General Butler, September, 1875. [13] Gold in its crude state, and uncoined, was until recently in use as money in some parts of California, Mexico, and on the West Coast of Africa. [14] Historically, bills of exchange probably originated with the Jews of the Middle Ages, who, ever liable to persecution, adopted a system of drafts, or written orders, upon one another, which each agreed to honor and pay to the person named in the draft.