Progress of Excavation.

Owing to the numerous sections of poor rock, interspersed throughout the work with stretches of sound rock, the progress of the excavation was very irregular, especially in 32d Street. The rate of excavation in good ground is shown in Table 1. In the sections of bad ground, the operations of excavation, timbering, and lining were often carried on alternately, and it is impracticable to include them in the table.

TABLE 1.—Progress and Methods of Excavation in Good Ground.

Thirty-Third Street.

Type of excavation.	Tunnels.	Worked from:	Dates.		Time elapsed, in days.	Length of tunnel excavated, in linear feet.	Average advance per day, in linear feet.	Methods and conditions.
Type of excavation.	Tunnels.	Worked from:	From	To	Time elapsed, in days.	Length of tunnel excavated, in linear feet.	Average advance per day, in linear feet.	Methods and conditions.
Full-sized single tunnel	B	1st Ave. shaft.	Feb. 28, 1906.	May 12, 1906.	74	346	4.7	Top heading and bench. Muck loaded by hand.
Full-sized single tunnel	A	1st Ave. shaft.	Feb. 28, 1906.	Apr. 30, 1906.	62	255	4.1	" " " " " " " "
Full-sized twin tunnel	A and B	1st Ave. shaft.	Aug. 23, 1906.	Jan. 5, 1907.	136	789	5.8	Top full-width heading and bench. Muck loaded by steam shovel. Working exclusively on this heading.
Full-sized twin tunnel	A and B	Intermediate shaft. (West of shaft.)	Apr. 4, 1906.	Oct. 31, 1906.	210	730	3.5	Top center heading and bench. Muck loaded by steam shovel. Working alternately in headings east and west of the shaft.
Full-sized twin tunnel	A and B	Intermediate shaft. (East of shaft.)	Apr. 4, 1906.	Oct. 31, 1906.	210	783	3.7	Top center heading and bench. Muck loaded by steam shovel. Working alternately in headings east and west of the shaft.
Full-sized twin tunnel	A and B	Intermediate shaft. (East of shaft.)	Nov. 1, 1906.	Dec. 26, 1906.	56	311	5.5	Top full-width heading and bench. Muck loaded by steam shovel working exclusively on this heading.
Exploration drift	A and B	Intermediate shaft. (West of shaft.)	Mar. 1, 1907.	July 23, 1907.	145	947	6.5	Exploration drift about 9 ft. by 12 ft. Mucking by hand. Fourteen timber bents were placed in March, and seven in April, 1907.
Twin tunnel. Enlargement of exploration drift	A and B	West shaft. (East of shaft.)	Sept. 6, 1907.	Dec. 4, 1907.	89	603	6.8	Drift excavated to full width and bench. Muck loaded by steam shovel.