Previous to the change in the hoisting apparatus, the monthly progress had averaged about 18-1/2 feet per month. The advance in October and November was 46 feet; the gain over the previous rate of progress is attributable to the practice of simultaneous blasting. On the first day of January, 1867, the shaft had been sunk 393 feet, leaving for excavation 644 feet. _Table showing the progress at Central Shaft from November 1, 1865, to December 1, 1866._ ======================================== DATE. | Distance | Progress. | down. | ==================+==========+========== Nov. 1, 1865, | 200.8 | Dec. 1, 1865, | 220.1 | 19.3 Jan. 1, 1866, | 232.5 | 12.4 Feb. 1, 1866, | 250.7 | 18.2 Mar. 1, 1866, | 264.1 | 13.4 Apr. 1, 1866, | 280.9 | 16.8 May 1, 1866, | 297.1 | 16.2 May 5, 1866, | 300.5 | 3.4 June 1, 1866,[A] | 300.5 | July 1, 1866,[A] | 300.5 | Aug. 1, 1866,[A] | 300.5 | Sept. 1, 1866, | 311.9 | 11.4 Oct. 1, 1866, | 331.1 | 19.2 Nov. 1, 1866, | 354.0 | 22.9 Dec. 1, 1866, | 377.0 | 23.1 ======================================== [A] Work suspended to put in new hoisting apparatus. The present hoisting apparatus is expected to be sufficient to finish the shaft. It has two wire ropes, each 1,260 feet long. The time for a round trip is seven minutes. The engine here is of 100 horse-power. The blacksmith shop contains two forges. At the small machine shop the repairs required here are made, as also some repairs for the West Shaft. The Central Shaft, though designed to aid in ventilating the tunnel, was intended also to accelerate its construction by affording to the process of excavation four faces instead of two during some portion of the work; and the former chairman of the commissioners expected by the aid of machine-drilling, the shaft might be completed in one year from the time such drilling should commence within it. In this anticipation, ten vertical drilling machines were constructed to work in the shaft area and a compressor with two cylinders was provided to furnish the power for operating them. The want of drilling machines at the East End became so urgent, that these vertical ones were changed to horizontals, and used at that point, and the sinking of the shaft by hand-drilling still continues. But if the experiments now in progress at the East End with the new drilling machine shall demonstrate its superiority over hand labor, the machine will doubtless be introduced into the shaft. WEST SHAFT. This shaft has an area of about 8 by 13 feet, and was excavated by Messrs. H. Haupt & Co. Its depth is 316 feet.