case, the method adopted should be tested by practical experiments, which will also in a great measure be dependent on local conditions.

It is not good metallurgical engineering to adopt an expensive process that in a short time may become worthless on account of such a change in the character of the ore as to require its abandonment for some other; yet the West is dotted with just such near-sighted experiments, which would not have occurred had some metallurgical engineer been called in to treat the ore experimentally before the mill was erected.

9. A fourth hydrometallurgical process consists in the reduction of minerals by chemical solutions. The factors entering into such processes, if not well known and recognized, will cause failure. It is seldom that an ore can be obtained which does not require some preliminary treatment before leaching, and in some cases the preliminary treatment becomes a part of the chlorination and Russell processes. In nearly every case, except that mentioned, where tailings are treated, crushing precedes leaching. In case the ore is refractory, roasting must precede cyaniding; and it is an absolute necessity where chlorination is practiced on sulphurets. There are other chemical processes that have been conditioned to the metals they are to extract, such as the leaching of lead, zinc, and copper ores. So far, they

have not come into general use because the expense connected with the recovery of the last-named metals by leaching their ores, with other necessary treatment, amounts to more than the value of the metals after recovery.

Lixiviation is defined as a process by which a soluble alkali or saline compound is extracted from an earthy mixture by washing out. As this does not cover the case of such metals as native gold, silver, or copper, the definition must be adjusted to include the term leaching, by which is meant the separation of soluble matter by percolation or drainage. The distinction between lixiviation and leaching would then be that the former was a process and the latter

a part of that process. A further distinction can be drawn from the fact that lixiviation includes dissolving with special solutions, while leaching is a matter of draining off the matter dissolved.

10. Ore Dressing and Milling.-The definitions given show that the four different hydrometallurgical processes mentioned require different milling methods and that their subdivisions also require different apparatus to carry out the particular processes involved. As an illustration, the cyanide mill requires very different arrangements and machinery from a chlorination mill, but since nearly every kind of apparatus that is used in hydrometallurgy has been discussed in Ore Dressing and Milling, it is unnecessary to go into the details of their construction and workings. the case of that metallurgical apparatus which is to be described under particular headings, such as tanks, barrels, pumps, filter presses, etc., it would simply be an unnecessary repetition to describe them at this time. Their description is given under the processes in which they are employed and which are included in this Course.

In

11. Roasting furnaces are described in Roasting and Calcining Ores. These form a very important adjunct to milling and smelting arrangements, few metallurgical plants being able to do without them. They are, therefore, mentioned, but not described in detail.

12. The question of water supply enters into the subject of mill location, and if not always for power, at least for milling and smelting purposes. In some cases it may be the only means available for power, and in any case no mill or smelter can be run successfully without a supply of water. The subject of water supply for power has been fully discussed in Hydraulics and Hydraulic Machinery.

13. Economic Arrangements.-In case there is not sufficient water to furnish power, but fuel for steam boilers is available, the position in which the steam boilers are to

be placed at the mill is one worth consideration. The situation of the engine room will be a matter of some moment for the reason that line shafting and belting must, as a usual thing, extend to various remote parts of the mill. The more distant it is from the power, the more difficult it becomes to maintain and keep it in repair. If it is possible to arrange

a mill so that fuel may be delivered direct to the boiler house, considerable labor will be saved, and if by the expenditure of $1,000 the labor of one man can be saved, it will prove economical in the end. At small works, where it costs 20 cents per ton to load, cart, and unload coal, and this is in most instances a low figure unless done by contract, a saving of $146 per year can be accomplished when 2 tons are used daily, provided the delivery track can be laid directly to a trestle adjacent to the boiler room.

14. In the arrangement of a mill, ore delivery is probably one of the most important items. If it is possible to place the mill near the mine whose ore is to be treated, an ideal location would be a side hill, provided the ore could be delivered at the top of the mill. In a situation of this kind. gravitation can be made to assist and thus avoid the expense of raising the material. Advantages of this kind would not always apply to those mills that use driers before crushing and screening.

Calcining furnaces are sometimes built high up in a mill, but there is less danger from fire and they are generally better located with regard to fuel and general handling of hot material if they are on the lowest floor of the mill. Even in case it is advisable to drop the ore to the drying furnace, there still remains certain advantages if a side hill is used for a mill site, as it usually furnishes a tailing dump, besides affording easy methods for dealing with slimes, tailings, and exhausted liquors.

15. Should the ore be delivered to the mill in lumps, so that it requires crushing, it is considered by some to be a disadvantage to have the mill on a side hill. This objection

arises from the fact that some one once placed a crusher at the top of the mill, without first making allowance for vibrations and thrust from loaded ore bins, besides not properly anchoring the crushers. Some will smile that such claims should be advanced as a drawback to placing the crusher at the top of the mill; nevertheless, the position of the crusher is one that requires serious thought and much careful expert work, in order to obtain a firm foundation and prevent excessive vibrations. If the crusher or the stamps cause a water tank to vibrate in unison with them, the building will be seriously affected and weakened to its foundations.

16. In case the mill is to be built on comparatively level land, the location should be chosen first with preference to the ore supply and then with reference to transportation of products and the delivery of fuel. In case it is to be a custom mill, similar preferences should be shown. The disposition of tailings is very important, but, like the water supply, it is considerably more flexible than the delivery tracks at a mill. The ideal location for a mill that must receive ore from different mines would be the brow of a hill, where the water supply might reach it by gravity, ore be delivered into bins from railroad cars, and tailings leave the mill in such manner that the expense of handling them would be practically nothing. There are instances where mills have been very favorably located, but it is simply impossible to find every advantage in one mill.

17. In case the mill can be run by water-power furnished by some stream in the vicinity, it may be advisable to transport ore to a mill so located. On the other hand, it may be advisable to locate the mill near the mine and transmit the power generated by water to the mill. This second arrangement would cause a great loss of power, but it may so happen that the location of the water-power was practically inaccessible to transportation facilities and mill construction. There are several instances on record where the power has been carried to the mill in the form of electrical energy.

LAWS RELATING TO WATER RIGHTS

DITCHES AND WATER

18. The laws passed by the United States Congress to encourage mining and assure to çitizens agrarian rights are given in the following sections as far as they have bearing upon water rights, mill sites, etc.

"Whenever, by priority of possession, rights to the use of water for mining, agricultural, manufacturing, or other purposes, have vested and accrued, and the same are recognized and acknowledged by the local customs, laws, and the decisions of the courts, the possessors and owners of such vested rights shall be maintained and protected in the same; and the right of way for the construction of ditches and canals for the purposes herein specified is acknowledged and confirmed; but whenever any person, in the construction of any ditch or canal, injures or damages the possession of any settler on the public domain, the party committing such injury or damage shall be liable to the party injured for such injury or damage."-Sec. 9, Acts of Congress (A. C.), July 26, 1866.

19. Excepted in Patent.-"All patents granted or preemption or homesteads allowed shall be subject to any vested and accrued water rights, or rights to ditches and reservoirs used in connection with such water rights as may have been acquired under or recognized by the preceding section."-Sec. 17, A. C., July 9, 1870.

20. Claims Subject to Ditches and Flumes.—“ All mining claims now located, or which may be hereafter located, shall be subject to the right of way of any ditch or flume for mining purposes, etc. Provided always, that such right of way shall not be exercised against any location duly made and recorded, and not abandoned, etc. without the consent of the owner, except by condemnation, as in the case of land taken for public highways. And provided further, that such ditch or flume shall be so constructed that