Slike strani
PDF
ePub

is much greater with us, by reason of the higher wages. But, if time is money, as it certainly is in such a case, the higher cost may be more than balanced by the greater speed.

The criticisms in which I have indulged concerning the general ineffectiveness of hand labor in this district should, no doubt, be modified by many individual exceptions. One remarkable and interesting case deserves special mention, namely, that of a gang of Italian laborers, who were set to take down the roof or top-heading by hand, after the main heading had been driven by machine drills. This top-heading had the whole width of the adit and was one meter high. The workmen developed surprising skill and endurance in drilling vertical upward holes, the drill being upheld and set by the holder, while the striker, in a standing position, swung the sledge, weighing ten to fourteen pounds, and delivered the blow upwards at the end of the swing. In this way forty-seven meters of linear progress was achieved in the last nine weeks, or a little over five meters per week, in the ordinary Frieberg gneiss. This rate was much in excess of that which had been previously achieved with German workmen; but it must be noted that, beside the peculiar method and perhaps greater activity or willingness of the Italians, they used dynamite, which the natives had disliked to employ. Two or three holes sufficed to take down the section of two meters across the adit.

The following table gives an outline of the progress of the work since the commencement. From the mouth of the adit to the first air-shaft the rock is a sort of clay slate. The rest of the adit is in gneiss. There is no timbering. The adit stands in solid rock, except at the intersection of veins, where it is protected by brick or

stone masonry.

The work, down to the end of 1875, was done exclusively with hand labor and common powder. Generally, a gang of 15 men (five in each shift of eight hours) was employed. Occasionally this number was increased, even as high as twenty-eight men, distributed in six-hour shifts. The work done with the aid of the machine drills required two Burleigh drills, one of which was held in reserve, and nine men in three shifts. Two shifts worked with the machine drills, and one by hand in the top-heading.

The data for the following tables are gathered from two volumes of the Jahrbuch fur das Berg-und Huettenwesen im Koenigreiche Sachsen. For the transformation of meters into feet, I am indebted to Mr. H. S. Drinker, who, having thus rearranged the table for his

[blocks in formation]

TABLE I.-MONTHLY PROGRESS OF THE ROTHSCHÖNBERGER ADIT, FREIBERG, GERMANY (HAND-LABOR, WITH BLACK POWDER).

Auxiliary

Mouth.

First Air Shaft.

Second Air Shaft.

Third Air Shaft.

Fourth Air Shaft.

Fifth Air Shaft.

Sixth Air Shaft.

Eighth Air Shaft. Seventh Air Shaft.

Shaft.

[blocks in formation]

1847 689 0 210

124.6 38 1848 287.4 86 104.9, 32 1849 354.3 108 127.9 39 1850 347.7 106 279.1 85

[blocks in formation]

1851 364.1 111

1852 252.6 77 1853 279.1 85

1854 298.8 91

1855 262.5) 80
1856 295.5 90
1857 318.5 97
1858 337.9 103
1859 331.3 101

1860 282.4 86 1861 286.0 88

32.8 10

[blocks in formation]

9.8

3

282.4 86

275.4 84

172.9 53

59.0 18

59.0 18

213.3 65

200.0 61

328.1 104

226.4 69

354.3.100

210.0 64

196.9 60 124.6 38 269.1 82137.8 42

282.4 86

137.8 42

318.5 97

275.8 84

167.3 108 173.9, 51

216.6 60183.8 56 118.0 36

269.1 82

272.5 83

[blocks in formation]
[blocks in formation]

98.4 30 111.5 34 19.7 6 85.3 26

26.21 8

13.1 4

[blocks in formation]

39.3 12

85.3 26

137.8 42

127.9 39

131.2 40

32.8 10

124.6 38

177.2 54

173.9 53170.6 52

190.4 58

157.5' 48 137.8 42

196.9 60

9.8 3

95.1 29

59.0 18

111.5 34

42.6 13

101.7, 31

9.81

3

65.6 20

[blocks in formation]
[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

6.6

2

13.2 4

[blocks in formation]

36.1 11

203.4 62

213.3 65

187.1 57

206.7 63

206.7 63

193.6 59

114.7 35

......

239.5 73 203.4 62 62.3 19 55.7 17

216.6 56

62.3 19

259.2 79 59.0 18

344.4 105

206.7 63

179.5 55

328.1 100 259.2 79

[blocks in formation]

213.3 65 255.8 78229.6 70 196.8 60 23. 7 9.8 3 246.0 75

[blocks in formation]
[blocks in formation]

5722 1744 748 228 3255 992 2421 738 3002 915 2333 711 1598 487 4036 1230 3117 950 2435 742 4426 1349 1056 322 1938 591 3812 1162 1771 540 173.8 53 121.3 37

318

97

33.8 124.7 38 191.5 58.3 220.1 67.1 230.9 70.4 179.5 54.7 159.8 48.7 175.5 53.5 119.9 36.5 101.5 30.9 184.5 56.2 117.3 35.8 193.8 59.1 158.8 48.4 110.7 33.8 86.9 26.5 60.7 18.5

71 21.6

ོས་སོ།ཚེ

[blocks in formation]
[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

forthcoming work on Tunnelling, kindly returned it to me with permission to employ it in its present form.

TABLE II-ANNUAL EXPENDITURES AND NUMBER OF WORKMEN EMPLOYED
ON THE ROTHSCHÖNBERGER ADIT, FREIBERG, SAXONY. EXPENDITURES IN
THALERS: ONE THALER =
72 CENTS U. S. GOLD COIN, NEARLY.

[blocks in formation]

It is a curious fact (if it be a fact), mentioned by the orator at the recent celebration, that the machine-drill was originally a Freiberg invention, and was tried long ago, without satisfactory results, in this very adit. Now, after making the tour of the world (though not "in eighty days"), it returns, perfected by the skill of American engineers, to win a conspicuous triumph on the scene of its early defeat.*

In concluding this brief and partial notice of a great work, I can merely give a few hints as to its extent and value. At the time of the final connection with Himmelfahrt, the Roschönberger adit and its branches to Himmelfahrt, Herzog August, Junge Hohe Birke, Beschert Glück near Zug, Einigkeit and Vereinigit Feld at Brand, and Himmelsfürst at Erbisdorf, comprised a continuous completed length of nearly 43,000 meters. Additional extensions of the main adit, amounting to 4300 meters, are still to be made, and branches to the government mines Isaak, Churprinz, etc., which will aggregate about 3627 meters more, making a complete length for the adit and its branches of 50,900 meters, or 31.6 English miles. This will be the longest adit in the world. The cost thus far has been over

* Since the reading of this paper, my attention has been called, by Mr. H. S. Drinker, to the fact that Couch, of Philadelphia, invented the first percussion drill 1849, and that Fowle's direct-acting drill was invented in the same year. I have not the precise date of the trial at Freiberg, but I feel sure it was later. R. W. R.

2,000,000 thalers,* or say $1,500,000 gold, which would be something over $51 per running meter. Assuming this sum to have been expended in equal instalments of 60,000 thalers through thirty-three years, and calculating compound interest at 4 per cent. annually, we have as the total cost,

[merged small][merged small][ocr errors][merged small]

a being the annual payment, r the rate of interest, and n the number of years. Putting a= 60,000 thalers, n = 33, and r = 0.04, m becomes in round numbers $3,972,600 thalers, or say $3,000,000. The cost of the adit has, therefore, been doubled by the delay. It is evident, on this showing, that "time is money" in an enterprise of this kind; and the moral of the calculation is still more strongly enforced when it is remembered that the long delay in the completion of the work has prevented the commencement of a productive industry, in comparison with which the loss of a few thousands in compound interest becomes trivial.

This adit drains the different mines with which it is connected to a depth from 94 to 152 meters below the deepest drainage adits. formerly possessed by them. It, therefore, relieves the existing machinery from lifting water to that extent, and also furnishes that amount of additional fall, to be utilized by subterranean water-wheels or hydraulic engines, after the manner of the excellent system long practiced in the Saxon districts. It is estimated that the power thus saved on the one side, and directly furnished on the other, amounts to 1100 horse-power. This gain is enough to justify the expenditure; but a further element of profit, which cannot be accurately estimated, will be furnished by the reopening of numerous mines and the development of deeper levels in those now working, for all of which the adit will supply, without additional cost, the means of inexpensive drainage, and, to some extent, of natural ventilation also.

If the economical Germans are willing to spend so much money, and make an adit thirty miles long for the sake of gaining from 300 to 500 feet in depth of drainage, it is evident that the age of deep tunnels is not over; and those engineers who have expressed doubts of the usefulness of the Sutro Tunnel, which will, with its branches, not exceed nine miles in length, and which penetrates the Comstock mines at nearly 2000 feet below surface, may find reason to revise their views.

This estimate was made before receiving the data concerning the expenditures of 1874 and 1875, which are included in the table. The argument holds good, though the amounts are smaller than those actually expended.

GRAPHIC METHOD OF KEEPING THE RECORD OF WORKING OF A BLAST FURNACE.

BY WILLIAM KENT, M. E., PITTSBURGH, PA.

(Read at the Amenia Meeting, October, 1877.)

IN a paper by Mr. Frank Firmstone, published in vol. iv, of the Transactions of the Institute, on "Comparison of Results from Open-topped and Closed-topped Furnaces," the regularity of the average grade of pig iron produced by the furnace under different conditions is expressed by means of a curve or diagram.

The object of this note is to show that the graphic method, or that of representing variations by plotted curves or diagrams, is capable of a much more extended application to blast-furnace records, making a valuable auxiliary to the "furnace book," and that by it the practical metallurgist may obtain at a glance information concerning the variations of the furnace during long periods, which could be found in the furnace book only after a tedious search.

Plate XII is a graphic record of an anthracite blast furnace for one month. The table on page 554 gives the figures obtained from the furnace book, together with a record of temperature of the atmosphere, barometric pressure, and moisture in the air, which was obtained from a meteorological observatory not far from the furnace.

In the records of a furnace, two of the variable qualities are final results, viz., the quantity of pig iron produced, and its grade; all the other variables are antecedent causes which produce the final results. Of these variable causes which contribute to the quantity of product and its grade, some are partially under the control of the furnace manager, others depend upon the state of the atmosphere, and still others are accidental. Of the first class are the character of the materials charged, and their relative proportions, their mechanical conditions, as wet or dry, large or small pieces, etc., the revolutions of the engine, the heat and pressure of blast, and the distribution of the charge. Of the second class are the number of pounds of air blown into the furnace for each stroke of the engine, the amount of moisture in the air, and the condition of the chimney draughts. These vary largely with the season of the year. Of the third class is the leaking of a tuyere or a temporary stoppage.

To keep a record of this kind for a whole year, it is only necessary to procure a sheet of common profile or cross section paper, about 38 inches long and 8 or 10 inches wide, with cross lines ruled about 0.1 of an inch apart. The vertical lines, or those in direction of the

« PrejšnjaNaprej »