skilled miners cannot be readily obtained. It requires but very few footings for bearings, and it can all be manufactured to order by the skilled mechanics at the shop, with the application of machine tools. For the security of the timbers dividing the shaft, or for the support of the guide rods, iron stops are bolted between the channelled iron at the proper places (Fig. 1), and for still further rigidity the same

Fig. 2.

10

口

studs are used in all the corners as in the cast-iron tubbing. In Germany, where iron has already been used for such purposes in the mines for a number of years, the experience in regard to cost has been, that wherever replacement of timber is required twice during a given period of time, iron supports are found to be the cheapest, and cheaper even than masonry, for the iron can be used over again, and always has some value. In running or heaving ground it answers better than any other kind of support, and is therefore much used now in the coal mines of Germany. The shaft is divided into two hoist-chambers and one air-chamber, bratticed air-tight. The hoist-chambers are fitted with 5" x 6" wooden guide-rods to guide cages, which will be provided with parachutes and safety-hooks.

the

The cages will receive a one-ton car, and are calculated to be raised, and the cars exchanged in one minute's time. The surface plant of this mine, when fully completed, will consist of (see accompanying map):

1. A shaft-house and derrick or pit-head, 38 ft. square, and 47 ft. high to axle of sheaves, is built of plain substantial timberwork in the pyramidal shape, strongly braced and weatherboarded throughout. 2. An engine-house, 42 ft. x 39 ft. in the clear, 19 ft. high, built of brick. It will contain a double cylinder direct-acting engine, 18 in. cylinder, 34 in. stroke, supplied with link motion and conical drum of 12 ft. and 7 ft. 6 in. diameter, with a band brake. A single engine of the same dimensions for working a Guibal fan, 12 ft. diameter, connected with the shaft by an underground archway. This will also supply the power for the mills to grind the salt for local trade, and drive an endless rope to transport the salt across the river to the harbor, as represented in the topographical sketch plan. The remainder of the engine-house is reserved for the air-compressors which will be used to run the diamond drills, and afterwards, probably, the salt-cutting machines underground.

3. A boiler-house, 34 ft. 6 in. x 36 ft. in the clear, 21 ft. high, containing four flue boilers 5 ft. diameter, 16 ft. long (68 flues 3 in. each), water reservoir, heater, and feed-pumps. This building and a chimney, 65 feet high from the grate, are built of brick in a substantial manner. Whenever the mine is ready to produce salt, the following buildings are designed to be added:

4. A reservoir-house, to dissolve impure salt contaminated by rock, for evaporation and supply of chemical works, which may be added to make soda by the ammonia process.

5. A mill-house for two pairs of breakers and four pairs of runners to grind the salt to the various grades required for market, and also to grind the impure, particularly gypsiferous, salt for agricultural

purposes.

6. Two evaporating-houses, to make salt by the boiling process for table use, if it should be required.

7. A coal-house, to stock a supply of fuel for the winter season. 8. A double track bridge, about 500 feet long, to transport the salt from the mines to the harbor, and the coal to the mines by means of endless ropes.

9. The loading bunks, to keep sufficient stock on hand to load vessels at short notice. These will be placed in the northwest corner of the harbor.

10. Chemical works, to make soda by the ammonia process. The location of these buildings, as also a boarding-house for thirty workmen, already built, will be noticed on the map.

The shipping season in this section of country being only about seven or seven and a half months in the year, the capacity of the shaft must be such as to raise 1200 tons of rock salt in twenty-four hours during the season. The mine cars of a capacity of one ton must therefore be raised and exchanged in one minute from a depth, if need be, of 1100 feet.

The track of the Grand Trunk Branch Railroad, it is anticipated, will be extended to the bunks alongside the harbor, so that railroad transportation may be secured the whole year round.

Conclusion. In presenting the subject of this paper to the Institute, I cannot refrain from calling particular attention to its importance. The great increase in the production of salt which can be noticed abroad, and particularly that of rock salt in several of the German States, show the great advantage of mining it over its manufacture from brine, except where fuel and transportation are as favorable to the latter manufacture as in England. The smaller amount of manual labor needed in mining, as compared with manufacturing from brine, particularly for the United States, is also an item which recommends itself to notice, as docs also the large amount of salt still imported into the United States. Various sections of country where salt is produced comparatively cheaply, cannot extend their area of supply for any considerable distance, owing to transportation charges.

It is a noteworthy fact that even now the rock salt of Stassfurt is being introduced in some of the Atlantic States of this continent, and is there competing with English salt for all purposes for which it can be used.

Attention should therefore be directed to an investigation of these points in the United States and Canada, where rock salt is likely to exist. Free use ought to be made of the diamond drill for exploration as the quickest, most economical, and most reliable means to obtain the necessary data, and, where circumstances are favorable, the mining of rock salt ought to be introduced instead of the manufacture of salt from brine.

GODERICH, October 10th, 1877.

THE LATE OPERATIONS ON THE MARIPOSA ESTATE.

BY CHARLES M. ROLKER, E. M., RENO, Nevada.

(Read at the Philadelphia Meeting, February, 1878.)

THE Mariposa estate, a grant made by the Mexican Government to Juan B. Alvarado, during the time when California was still under the dominion of Mexico, was purchased in 1847 by J. C. Fremont, and the United States patent issued to him in 1856. By sale, or its equivalent, money advanced, the property came into the hands of the Mariposa Company, June 25th, 1863, and through a varied existence of work and temporary inactivity, has as yet been kept as an undivided property, and rests at present with the Mariposa Land and Mining Company of California. I pass over this period of 15 years without giving the history of the ups and downs of the estate, partly because it is familiar to many, and also because I think in such a case this paper would assume too much the character of a narrative.

The estate is situated in Mariposa County, California, about 170 miles southeast of San Francisco. It begins in lat. 37° 26' 38" north, and long. 119° 55' west, and runs 6 miles north; thence 6 miles west; thence 5 miles northwesterly towards the Merced River; thence 8 miles southerly; thence 3 miles easterly; thence 1 mile southerly; thence 2 miles easterly; thence 2 miles southerly; thence 2 miles easterly; thence 1 mile southerly; thence 2 miles easterly; thence 1 mile northerly, and thence 2 miles easterly to the place of the beginning; embracing 44,387 acres (70 sq. miles) more or less.

To describe this vast estate in detail as to its full geology, its numerous quartz veins, its many facilities to exploit them and work them by cheap methods, would lead me further than I intend to go at present, and I will content myself to describe the latest workings of the company and its immediate field of operations.

As long ago as 1860 the late Dr. Adelberg advised the running of an adit from the northwestern edge of the estate at Benton Mills on the Merced River. His object was to undercut the deepest workings of the then paying mines on the estate-the Pine Tree and Josephine. Following this advice, the tunnel known as "River Tunnel" was commenced. Its entrance is in S. 5, T. 4, S. R. 17 E. It is run in

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