Page:Whymper - Scrambles amongst the Alps.djvu/99

Rh "In April, the improvements introduced, and the practice acquired, caused better progress, and in the middle of the month the work of perforation was accomplished in eight or nine hours."

"In the month of May, when nine perforatrices were at length at work, progress was stopped by exterior causes, and was suspended for two months."

"From July to the 19th of August the work was continued, but only one attack per day was made, on account of there not being a sufficient number of instructed persons to carry on the work incessantly. Still it was carried on with regularity, and the advance was 28 inches to 3 feet per day. The perforation was generally accomplished in six hours."

"From the 19th of August the work was continued day and night, but at first, in consequence of the inexperience of some of the employées, the depth of the holes had to be reduced to two feet, and that depth occupied them twelve hours. Little by little this fresh band of workmen became as skilful as the first, and at the end of two months the two attacks were carried on with regularity." The best form of boring-rod for all kinds of rock, excepting such as are homogeneous, was hit upon in 1861, and it has been in use ever since. The head is in the form of a Z. For homogeneous