Experiments have lately been made with the above machine, which leave no doubt of its superiority for obtaining the greatest amount of gold from a given quantity of quartz. These experiments have been con ducted at the Novelty Iron Works in this city, and the working of the machine has fully borne out its character for efficiency and eco nomic results. A public trial of its capabili ties of performance, was made last week at the above-mentioned establishment, under what may be called the most disadvantageous circumstances which resulted in a perfect suc cess. The experiment was made with the refuse from the workings of the Gold Hill Mining Co., in North Carolina, which are technically called " tailings," and thrown aside as worthless, alter all the gold has been or is supposed to have been extracted. With some of these ' tailings," large quantities of which have been bought up, we understand, by par ties in Boston for further extraction of the re maining gold, the efficacy ot Berdan's machine was tested. The quantity of " tailings " ex perimented with was two barrels, weighing together about 100 lbs,, and to these were added about 10 lbs., or rather more of quick-silv er, the processes of pulverizing and amal gamation being carried on together, which will be understood by referring to page 35 of the present volume of the Scientific Ameri can, where the machine will be found illustra ted, with accompanying letter-press explain ing its mechanism and method of operation. The proceeds were 58dwts. 1 gr. of gold, but as the experiment was done very roughly,a deduc tion must be made for impurities which would be thrown off on refining ; these, however, on examination of the specimen, we should con clude will not amount to much; at all events it proves decidedly that the refuse of the above amed mine is worth being washed over again, the weight of gold obtained from the above quantity ot " tailings " being sufficient to amply reward for the expense and labor in extracting it. A second experiment of crush ing the quartz as well as pulverizing it, was afterwards made 70 lbs. of gold-bearing quartz, from a mine in Rutherford Co., in the same State, being operated upon j in this in stance the product was very small and mixed with interior metal, bearing no comparison with the results obtained by the first experi ment. We will not vouch for its accuracy, but it was publicly mentioned, during the ex periment, that the per centage of precious me tal obtained from these " tailings " was great er than that obtained at first from the origi nal quartz. Whether this is the case or not can be easily ascertained, the quantity obtain ed by the above experiment being knowni and the quantity obtained from a given quan tity of quartz by ftie Gold Hill Mining Co. being compared with the former.