| |
Twin tunnel. Enlargement |A and B | West shaft. |
of exploration drift | | (East of shaft.) |
=============================+========+=====================

======================================================================
4 | 5 | 6 | 7 |
----------------------------------+--------+------------+------------+
| | Length | Average |
DATES. | Time | tunnel | advance |
----------------------------------|elapsed,| excavated, | per day, |
| | in | in | in |
From | To | days. |linear feet.|linear feet.|
----------------------------------+--------+------------+------------+
Feb. 28, 1906. |May 12, 1906. | 74 | 346 | 4.7 |
| | | | |
Feb. 28, 1906. |Apr. 30, 1906. | 62 | 255 | 4.1 |
| | | | |
Aug. 23, 1906. |Jan. 5, 1907. | 136 | 789 | 5.8 |
| | | | |
| | | | |
| | | | |
Apr. 4, 1906. |Oct. 31, 1906. | 210 | 730 | 3.5 |
| | | | |
| | | | |
| | | | |
Apr. 4, 1906. |Oct. 31, 1906. | 210 | 783 | 3.7 |
| | | | |
| | | | |
| | | | |
Nov. 1, 1906. |Dec. 26, 1906. | 56 | 311 | 5.5 |
| | | | |
| | | | |
| | | | |
Mar. 1, 1907. |July 23, 1907. | 145 | 947 | 6.5 |
| | | | |
| | |