hole was abandoned because it contained no value, or because, containing value, it could not be profitably worked. As we think of mines nowadays, we can conceive several reasons why, before the advent of transportation lines and the invention of modern metallurgical processes and many forms of labor-saving machinery now so common in and about mines, many very rich deposits may have been necessarily forsaken by their discoverers. But such a property would, if now worked, probably prove highly profitable. We thus note that there exists some elasticity in the meaning of the word mine. An unprofitable project at one time may develop into a mine at a later period. Many gold mines have become worthless propositions merely through changes in the ore that have rendered further work unremunerative.

II
WHAT IS MINING?

Having considered the accepted definition of a mine, let us now extend our reasoning a little and inquire just what is meant by mining. At first thought, one would say that mining is, in a broad sense, the art or practice of excavating, at a profit, the ores of metals, the beds of coal, the gravels of placers and the deposits containing precious stones. Are we justified in letting this definition stand as it is? If we do not make any change, we must exclude all quarries, sand banks, clay pits, and the numerous sorts of works that are producing the non-metallic minerals of commerce. Very well, since we find good usage will warrant us, we will do so.

Hackett Mine and Mill, Joplin, Missouri.

Still, there are other pertinent questions arising. Does the practice of mining cover the treatment of the excavated products? Here we run across a mooted point. The British and the American uses of the word mining seem to be a bit different in this regard. Upon the Rand, South Africa, a territory dominated by Englishmen, every mine is equipped with its own mill, and all notions of mining cover the inseparable idea of local ore treatment. Here, in our country, there are many, many mines which have absolutely no means of treating their own products and the managers give no thought whatever to metallurgical or milling lines. There are, on the other hand, many companies that have erected private plants at their mines for the extraction of metallic contents from the ores. Here it may, or it may not, happen that the operations of mining are considered as distinct from those of treatment. In some instances, as at the Tonopah Mining Company's plants, there is separate superintendence of the milling and the mining; but in the Joplin, Missouri, zinc region one superintendent looks after the running of a mine and its omnipresent mill.

There may be drawn a sharp distinction between what is really mining and what is the subsequent treatment of the ores for the extraction of values. The latter field is denoted Metallurgy when the operations are of such a nature as to actually recover or extract metallic products or metals. If the treatment process has for its object merely the rejection of some of the worthless materials in the original ore, thus causing a concentration of the valuable minerals, but without actually obtaining any metal, then the term Ore Dressing is warranted. At some mines, there is maintained a practice of culling out, often by hand, a certain percentage of the obviously worthless ingredients of the ore before shipping the products to treatment plants. This is neither milling, metallurgy, nor ore dressing, but is more properly called Sorting. It is one of the operations connected with mining. Milling may be either ore dressing or metallurgy.

In the operations of placering, there is a simultaneous excavation of a deposit and an extraction of the valuable contents. In this case, shall we call the process mining or metallurgy? If it is a gold placer, one may see the recovery of the metallic values. Here, the usage of the majority of practical mining men will uphold us in always speaking of the work as mining.

In its original significance and use, metallurgy involved the use of fire for the concentration and recovery of metals. With recent advances in chemistry, there have been numerous discoveries of wet or fireless methods for arriving at equivalent results, so that it is now perfectly proper to allow the word metallurgy to cover such processes as cyanidation, chlorination, electrolysis, and the host of new inventions that are continually appearing.

The writer has consulted a number of authorities on mining lines to ascertain just what sort of a position to give to the practice of ore dressing. Prof. Robert H. Richards, the head of the mining department in the Massachusetts Institute of Technology, and the inventor of machines which have made him famous among mining men, says, "Ore dressing is an essential part of mining. The whole object of ore dressing is to remove gangue before shipment and so save in freight and treatment charges." Mr. A. G. Charleton, the eminent English mining engineer and author of numerous books, in discussing this question, writes, "Personally, I am of the opinion that ore dressing should be included in mining." One has but to look through the catalogues of most of the American and foreign mining schools to find that little or no line is drawn between the courses in mining and metallurgy, and almost universally the dressing of a mine's product is taken up as an inseparable part of mining. In a very few exceptions, the courses of study are so planned as to draw an imaginary line between mining and metallurgy, and in these instances, ore dressing is placed with metallurgy only for convenience in the use and arrangement of college laboratories. But, since it is a common practice for mining companies to install plants right at the mines for the purpose of diminishing the bulk of ore shipped and to thus save in freight and custom treatment charges, mine superintendents and even the common miners have become accustomed to thinking of such plants as but units of the "mining" plants. At bituminous and anthracite mines whose products contain objectionable amounts of impurities, it is a common practice to subject the output to a Washing to remove the deleterious substances before shipment to the market.

Coal Washing Plant, Pana, Illinois.

In view, then, of these reasons, it is proper to decide that mining is a term broad enough to cover the operations of extracting coal and metallic ores from the ground and of preparing them for shipment or metallurgical treatment.

Coal is always coal, no matter in what thickness of deposit it is found. It may not be minable coal because in thin seams or because so intercalated with layers of slate or "bone," that the mine's mixture, or so-called "run of mine," is not salable. But with metallic ores, we run across an idea that is occupying the attention of many prominent geologists and mining men.

What is ore? This is a question to which there have been many attempted answers. There has been an evolution of ideas, with a corresponding gradation of definition. To set a uniform standard of thought upon this point, officers of the United States Geological Survey, a