practical laboratories will one day fulfill, and that is the carrying out of such experiments as will further improve the processes now in vogue. It is one thing to instruct our young men so that they can go West and handle the machinery now in use there; it is another thing, and an equally important one, to have machinery at our disposal somewhere where it can be run in a truly experimental manner, where truly scientific experiments can be made-by which I mean experiments so shielded from possible complexities and mistakes that the results shall be traceable to the proper causes. I may instance an investigation upon which I entered some years ago, in relation to the efficiency of stamps, calculated with regard to their speed, weight, and drop. Those three elements must have some definite relation to the efficiency of the stamp in the quantity it will crush. It does make some difference whether we drop a heavy stamp a certain distance or a light stamp, weighing half as much, twice as far. I have been for some time a partisan of lighter stamps and more rapid blows than have been the fashion in many parts of the country, and in investigating that question aud developing results, although I was able to eliminate from the problem such disturbing elements as depended upon the generation and transmission of power, I was not able to eliminate or perfectly estimate the influence of the facility and area of discharge, which has a decided effect on the quantity crushed, nor, on the other hand, the character of the rock, since in comparing different stamp-mills in different localities you have always to bear in mind that you are comparing them by different standards. Some quartz may crush and does crush easier than others. We inust throw out abnormal results on either hand. I have known 72 tons to be run in twenty-four hours through a 10-stamp mill. The average would be something like 123 to 15, and anything that varies far from that average in either direction might be fairly attributed to some abnormal quality in the rock. To make complete experiments of this kind you want to have all the conditions maintained except one. If you wish to test discharge, you want to use the same battery and the same quartz, and vary nothing but the discharge; if you wish to test the speed and the weight of the stamp, you must vary nothing but the speed or the weight. That is impossible when you come to collect the results of experiments in ordinary practice. You cannot ask the mill-man to vary the weight or speed of his stamps, or to keep taking different kinds of rock, and stop his running at short intervals and clean up with spasmodic frequency, just to suit your desires. Hence, it is almost impossible to get absolute results. I trust the creation of such laboratories as have been described to us in the paper just read will open the door to something like careful work of this character. A specimen of what I mean is furnished by the experimental investigation of the Washoe amalgamation, which was made under the charge of Professor Brush, Mr. Hague, and Mr. Daggett, on the ores of the Comstock lode, at the laboratory of the Sheffield Scientific School at New Haven. The results are published in the third volume of Clarence King's report. Another specimen of what I mean I have been fortunate enough to secure myself, through the assistance of Mr. G. F. Deetken, of Grass Valley, Cal., who has made a very thorough analysis at every stage of the California stamp-mill process. I think it is a question worthy the consideration of the faculty of this school whether some of the peculiar amalgamating-machinery employed in California might not with advantage be substituted for the simple amalgamation in battery and on copper plates, which is recognized in practice now to be a wasteful method. |