The Commissioners for the year 1868, report as follows:
During the Summer, Glycerin of a very good quality has been manufactured at this point, under the direction of Mr. Mowbray, and has been used for several months in blasting in the tunnel east of the West Shaft. No accident has attended its use. And while its effect in the heading did not meet the expectations of the Commissioners, the result of its operation in the bench below the heading, justifies the belief that with due provision for its economic use, and essential care and attention paid upon its management, it will prove an effective agent in the prosecution of this enterprise.
The Superintending Engineer, Benj. D. Frost, Esq., reports as follows: “The following is a statement of monthly progress.
| Length driven. | Total distance from W. Shaft. | |||
| In November, | 1867, | 33 feet, | 1272 feet. | |
| December, | 1867, | 22 feet, | 1294 feet. | |
| January, | 1868, | 33 feet, | 1327 feet. | |
| February, | 1868, | 35 feet, | 1362 feet. | |
| March, | 1868, | 34 feet, | 1396 feet. | |
| April, | 1868, | 24 feet, | 1420 feet. | |
| May, | 1868, | 26 feet, | 1446 feet. | |
| June, | 1868, | [3] | 21 feet, | 1467 feet. |
| July, | 1868, | (Nitro-Glycerin used) | 47 feet, | 1514 feet. |
| August, | 1868, | “ | 44 feet, | 1558 feet. |
| September, | 1868, | “[4] | 51 feet, | 1609 feet. |
“But for the improved methods of working introduced, the advance would have been much less satisfactory than that we are enabled to exhibit above.
“Concerning the employment of Nitro-Glycerin and machine drilling at West Shaft, it is hardly necessary to remark that many difficulties are to be encountered in the training of men to a new service and in successfully employing a new description of fuse and explosive. Some remarks upon our experience in blasting with this compound, will be found in a subsequent portion of this report. Continuous use of machine drills was commenced at the West Shaft in the latter part of June, and of Nitro-Glycerin as an explosive in the month of August. Some delays were necessarily experienced at first, but greatly improved progress was shortly attained. Some previous trials of machine drilling had been made earlier in the present year, but without continuous progress, upon which satisfactory estimates of success might be based. The last workings made, including the month of September, up to the time of suspension, about five-sixths of a working month, attained a linear progress of 51 feet, with six drills only. The machinery provided at West Shaft is only sufficient to supply the pneumatic power for the ordinary working of the above number, to which accordingly we have been necessarily confined.
The two drill carriages employed are larger than those at East End, and are intended to carry five drills each—in all, ten drills working at the breast of the heading. Assuming, as we may safely, that the rate of progress is proportional to the number of drills employed, ten drills would advance 100 feet per month; and with full power provided and further experience to be acquired by the workmen, this and even greater average rates of monthly progress can be made and maintained.
These headings are run at top, i.e., above the excavations hereafter to be made, and of such height, and top outline as to correspond with the roof of the completed tunnel.
Amounts of progress upon this section of the work during present and preceding year are exhibited in the following comparative table:—
| West Shaft | Heading and Adit. | Enlargement. | ||
| Section. | Linear Feet. | Cubic Yards. | Linear Feet. | Cubic Yards. |
| Year Ending | ||||
| November 1, 1867 | 543 | 2349 | 161 | 2100 |
| November 1, 1868 | 1280 | 4696 | 82 | 488 |