It is a singular fact that notwithstanding the large number of able mechanics that have emigrated to California, to engage in the development and extraction of its golden wealth, but few of them have produced any important inventions to assist their labors. Those who have had experience in gold digging have represented to us that miners have found great difficulties for the want of some process, by machinery or otherwise, in extracting the gold from the extraneous substances with which it is intermingled. In consequence of the neglect of inventors and mechanics to pro-Tide some quick means for the accomplish- i ment of this object, particularly in the ex- I tracting of the gold from the heavy black sand or iron oxyd with which it is found, a ' large amount of the combined mass is thrown ] aside as a refuse substance, although known to be rich with the precious metal. The Sacramento Union, in a late article on this subject, notices a method of extracting gold from what is termed as the " tailings" of the quartz mills, invented by a Frenchman named J. B. Chavelier, at present residing in Sacramento. These "tailings" are the sulphates, chiefly of iron, which, after pulverizing, are rejected in the amalgamating process, and thrown out generally as worthless by the miners. He found them to contain from fifty to one hundred cents of gold to the ounoe of sulphate, and succeeded in bringing his machine to such perfection as to enable him to work over a tun of the quartz waste per day, from which is yielded an average of $100 per tun—one thousand dollars being sometimes extracted from this material, which costs only thirty dollars in its almost refuse state. In addition to the sulphates, a considerable amount of mint and assay ashes are subjected to the searching process. But a larger business still is done in the black sand procured either directly from the miners' camps, or from the bankers, who obtain it in cleansing the dust they purchase. These "blowings," as they are denominated, are sometimes very rich, yelding as much as $210 upon fifty-seven ounces of sand. The use of the sulphate does not end with the surrendering up of its golden richness, but it is sold at three cents per pound, and converted into a common article of paint, which, after passing through the mill, is of a violet color.