object of experiment, or as incidental to other investigations), and to present them in a condensed form to the readers of The Popular Science Monthly.
Some of these experiments (notably those of Faraday) present the curious anomaly of revealing to the physical sense of sight particles of matter which are almost too infinitesimal for the mind's eye to conceive, thus seeming to reverse the order of scientific investigation which usually prolongs the mental vision far beyond the region of possible physical revelation.
The experiments to be described have been arranged in the following order:
1. On the natural dissemination of gold.
2. Beating into thin leaves.
3. Faraday's researches.
4. Depositing by the galvanic battery.
5. Vaporization by the electric spark.
Some years since a very interesting series of experiments was made by the late Mr. J. R. Eckfeldt, then chief-assayer of the mint at Philadelphia, and his associate, Mr. W. E. DuBois (the present incumbent), upon the "Natural Dissemination of Gold." The results were presented to the American Philosophical Society, in the form of a paper, by Mr. DuBois, and published in their "Proceedings" of June 21, 1861.
The precious metal was found disseminated in marvelously fine division through a number of substances where its existence had not been previously suspected.
In the clay of which the Philadelphia bricks are made, gold was found in the proportion of about forty cents' worth to the ton. Each brick contains a sufficient amount of gold to make a glittering show of two square inches, if brought to the surface in the form of leaf.
An estimate of the thickness of the bed of clay under the city revealed the startling fact that more gold lies securely locked up in it than has been procured, according to the statistics, from Australia and California. A specimen of galena from Buck's County, Pennsylvania, yielded gold in the proportion of one part of gold in six million two hundred and twenty thousand (6,220,000) parts of ore; not quite ten cents to the ton. The report of these experiments concludes as follows: "Of this we may be confident, that the atoms of gold are homogeneously and equably dispersed through the clay, or other matrix; but by what natural process or for what final cause these fine particles should be thus diffused, seems quite beyond the reach of human philosophy."
The remarkable malleability of fine gold was a property well known to the ancients. Homer refers to the art of gold-beating, and Pliny mentions that an ounce of gold was beaten into seven