Diamond Vein." In the Clayton tunnel, situated at Nortonville, the distance from the floor of the "Clark Vein" to the roof of the "Black Diamond Vein" is six hundred and ninety-six feet. The dip here being about 31°, it follows that the total thickness of the strata, including the Little Vein, between the Clark and Black Diamond Veins, is three hundred and fifty-nine feet. These veins are found throughout all the mines, the Clark Vein predominating.

THE CLARK VEIN.-This vein has been worked continuously throughout all the mines. It varies in thickness at different points, from a minimum of eighteen or twenty inches to a maximum of four and a half feet. The greatest variations in the thickness of this bed do not occur within the limits of the Black Diamond, the minimum being twenty-eight inches and the maximum being thirty-nine inches. As it extends east it grows thinner, and reaches in the S. W. quarter of section 4 a minimum of from eighteen to twenty-four inches. As it extends farther east to the S. E. quarter of section 4 it gradually increases in size, being at this point from three to four feet in thickness, and reaches its maximum in the Pittsburg mine, where it is four and a half feet. The Clark Vein is generally free from interstratification of slate or dirt of any kind, and with the exception of a portion near the S. W. corner of section 5, where it has been badly crushed by the moving and bending of the strata, it generally makes good clean coal. Its roof and floor are generally good, and require but little timbering, it being of good, solid sandstone.

The chief openings to the Clark Vein are the Black Diamond Company's openings, of which there are three. The first of these is known as the "Little Slope," the second is the "Mount Hope Slope," and third the "Black Diamond Shaft." Second, the "Union Company's Slope.' Third, the slope of the old Eureka Company. Fourth, the "Pittsburg Slope." Fifth, the "Independent Shaft."

The mouth of the "Hoisting Slope" of the Black Diamond Company is situated in the bottom of a deep ravine, which runs up southwesterly among the hills, and is eight hundred and thirty feet above low water mark on the San Joaquin River. This slope is ninety-eight feet long, and goes down through the Clark Vein at a pitch of about 35°.

The mouth of the "Mount Hope Slope" is situated about four hundred and fifty feet northeasterly from the mouth of the "Hoisting Slope," and is seven hundred and ninety-seven feet above low water mark on the San Joaquin River. This slope is two hundred and ninety-three feet long, to the Clark Vein, and has a pitch to the south of about 37° 15'. From its foot the "Mount Hope Gangway" runs east and west through the Clark Vein, and is over a mile in length.

The "Black Diamond shaft" is situated six hundred and twenty feet

northwesterly from the mouth of the "Mount Hope slope." It is vertical and its mouth is eight hundred and thirty-nine feet above low water mark. The mouth of the "Union Company's slope" is situated very close to the line between the S. E. and the S. W. quarters of section 4, and is eight hundred and sixty-six feet above low water mark on the San Joaquin River. The slope is four hundred and seventeen feet long to the "Clark vein," with a pitch of 37° 45′ to the south. From its foot a gangway runs east and west through the Clark vein.

From a point on this gangway, two hundred and forty-four feet west of the foot of this slope, a counter slope runs down, with a pitch of 28° 23′ to the north, three hundred and four feet to a second gangway, and then about three hundred feet to another gangway. The old Eureka slope was about two hundred and ninety feet long, with an average pitch of 43° 15' to the south; its mouth is seven hundred and eighty-six feet above low water mark.

The Pittsburg slope is in the southeast corner of section 4. Its mouth is eight hundred and thirty-eight feet above low water mark. Its pitch, 25° 50′ west of south, and is two hundred and forty feet long to the Clark vein. From its foot a gangway runs in both directions through the company's property. From a point on this gangway, twenty-five feet west of the foot of the Surface slope, a counter slope runs down on the dip about eight hundred feet, with a pitch of 31° 30'.

There are, however, two intermediate gangways, one at a point three hundred feet, and the other at a point five hundred and seventy-nine feet down from the head of the counter slope. In the eastern part of this mine and distant nearly a quarter of a mile from the foot of the surface slope, there is another counter slope running down from the upper gangway to the second one.

The Independent shaft is a vertical shaft sunk by the now defunct Independent Company, at a point a little S. W. from the center of the N. E. quarter of the S. E. quarter of section 4. Its mouth is seven hundred and nineteen feet above low water mark, and it is seven hundred and ten feet deep. This mine was worked at a great loss and was finally abandoned.

FAULTS AND DISTURBANCES. Throughout the Mount Diablo coal mines the beds are frequently more or less disturbed by faults and dislocations, some of them being of great magnitude.

These disturbances are generally most sharply defined in the Clark vein. The longest distance which occurs anywhere in the mines without any fault or disturbance of noticeable magnitude, is a distance of about two thousand feet on the Clark vein stretching east from the Black Diamond into the Union mine. Most of the larger faults of these mines have a northeasterly and southwesterly course, the plane dipping at a steep angle

to the northwest. With reference to the direction of those in the faults, the general law holds pretty well throughout these mines, that where the plane of a fault is inclined from the vertical, it is the hanging wall of the fault that has gone down. This law, though general, is not universal, as cases occur where the throw is in the opposite direction.

The general line of strike of the beds, in spite of all faults and disturbances, is very straight for a distance of nearly a mile and a half in a direction of about N. 86° E. from the Pittsburg slope, to a point about as far west as the middle of section 5, and within this distance the dip does not vary greatly from 30°, ranging in general from 28° to 32°. But going west from the middle line of sections 5 and 8 the beds and strata curve around in a gentle sweep to the south, while at the same time their dip diminishes until it does not exceed 20°.

The general form of the beds as they lie in this shape is that of warped surfaces, which produces a gradual increase in the height of all the lifts in going toward the west.

VENTILATION.-In mines situated as these are amongst the deep cañons and high hills, there is generally great difficulty in securing good ventilation, which is a necessary adjunct to the working of the mines. Artificial means have been resorted to, and not until lately with any success. The water being supersaturated to such an excess of Sulphuretted Hydrogen, that on exposure to the air it forms white deposits of sulphur, and the gas escaping causes a bad effect on the eyes. One method used at the mines for ventilation was the keeping of lighted fires at the bottom of the ventilating shafts, which heated the air and kept it in rapid circulation.

Chloride of lime was used for the purpose of decomposing and absorbing the deleterious gases, but it did not accomplish the work; its odor being very disagreeable, this method had to be abandoned finally. Then one of the largest sizes of Root's patent rotary blowers was obtained. This was driven by a small engine, the air was forced through a pipe down the Black Diamond shaft, and after its course through the mines, found its exit through the Mount Hope gangway. This method worked very well, but it was not complete. Another method was resorted to; instead of forcing the air down through the mines and out, this principle was reversed, and the air was exhausted from the mines; this was an improvement on the other, yet enough gas remains still to make it disagreeable to those working in them.

There is but little fire damp in these mines, yet occasionally a locality is found which requires close watching, but not enough shows itself to require the use of the safety lamp, this being used only as a test for the fire damp. Numerous small casualities have occurred from the presence of fire damp, which only resulted in the severe burning and occasionally in

the death of one or two men. But it was all owing to the gross carelessness of the miners going into those parts of the mines that had not been worked for some time, and where they might have expected to find the fire damp, if they had reflected but a moment.

PEACOCK AND SAN FRANCISCO MINES.-To the west of the Black Diamond Company's mines for a distance of a mile or two there has been considerable prospecting done in years past, but the above mines are the only ones worth mentioning. The "Peacock" mine is situated on the Black Diamond bed. The San Francisco mine is situated about half a mile west of the Peacock mine; this mine is also on the Black Diamond bed, but neither have been profitably worked.

CENTRAL OR STEWART'S MINE.-This mine is over the ridge and easterly from Somersville, and is situated in a steep and narrow ridge running east and west across section 10. It was originally opened by a tunnel, its length to the Clark bed being about one thousand feet. There are exposed in this tunnel beneath the Clark bed four distinct seams of coal of different thicknesses. In 1870 a gangway was driven in on the Clark bed two hundred and seventy-five feet east and three hundred and seventy-five feet west from the tunnel and considerable coal extracted, the bed averaging thirty-nine inches in thickness. Since that time a tunnel has been driven in Stewart's mine from the Clark bed northerly through the ridge, and to daylight on the other side.

EMPIRE MINE.-This mine is located on the southwest quarter of the southeast quarter of section 12, and is about four hundred feet above tide mark on the San Joaquin River.

What information we have been able to glean on this mine will be found in the History of Township Number Five.

TEUTONIA MINE.-Passing east from the Empire mine we come to the Teutonia mine, in the south part of the S. W. quarter of section 7, T. 1 N., R. 2 E., the mouth of the mine being about one hundred and fifty feet north of the section line. Considerable work was done on this mine and a large amount of coal was found, the seam being about thirty-six inches thick, but it was finally abandoned.

RANCHO DE LOS MEGANOS COAL MINES.-The mines on this ranch are situated just on the edge of the Mount Diablo foot hills, at a point some five miles easterly from the Mount Diablo mines, and at an elevation of about one hundred and sixty feet above tide mark on the San Joaquin

River. The parties who commenced to develop this property ran a slope from the outcrop down a vein about three and a half feet in thickness, and one hundred and seventy-five feet in length. The dip of the vein is about N. 35° E., and at an angle of 18° to the horizon. A shaft was then sunk one thousand three hundred and seventy-five feet N. 70° 45' E. from the mouth of the slope. This shaft is four hundred feet in depth, and was divided into three compartments, two for hoisting coal and one for pumping purposes. Some work has been done in the mine since, but it has not been operated for market purposes. The distance to a suitable landing on the San Joaquin is about seven and three-fourths miles. With this mine the Mount Diablo coal fields may be said to terminate. No indications worth mentioning show themselves until we reach the Corral Hollow coal field.

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