“Our first work was to examine and disclose the enemy lines of communication about the Castelletto and Tofana sides, and to gain full knowledge of their position in detail. In order to accomplish this, observation points were established which allowed us to carry out such investigation and to make topographical sketches of the zone. Being as we were always in the proximity of the enemy, this was a long and fatiguing work. After a month, however, we succeeded in constructing a series of positions at short distances from those of the enemy (from 50 to 150 metres). These were provided with cables and rope ladders to enable us the more rapidly and easily to study (from all possible points of vantage) the enemy’s positions and the development of his works. “The topographic work was begun by taking as a plan metric base measurement 116 metres of ground on a four-triangle table, which method enabled making all other drawings based on it. By basing our findings on this table, we were able to draw up a series of points of the enemy’s positions. Using the method of successive intersections, we thus obtained all points of interest to us, as regards direction, distance and height. “In addition to this work, executed with the greatest care and accuracy, we made two independent drawings of the enemy’s positions by simpler but less exact methods. The first was made with a topographic compass and Abney level; the other with a Monticole field-square. By these means we obtained excellent checks on the base system, and so grounded our work entirely on the trigonometric table and on the drawings by intersections. “From the middle of February to the end of March the tools used for piercing consisted only of mallets and chisels. Our progress was necessarily slow, yet it was sufficient in this time to give us, besides 14 metres of tunnel, room for installing the perforating machinery. At the end of March, notwithstanding heavy snowstorms, the machinery--some pieces of it weighed as much as 500 and 600 kilos--for beginning work was installed. This was all brought up by hand, and without incident. “The mechanical work was begun on April 2. We utilised two plant as follows: “(1) A complete group of benzo-compressors, consisting of a 30-40 horse-power kerosene motor adjusted to a Sullivan compressor by means of a belt. This machinery was installed, on a solid base of cement, at the beginning of the tunnel, in a 5 × 8 metre space dug out in the side of the mountain for that purpose. “(2) An Ingersoll compressor mounted on a four-wheel truck. “Both machines were of American manufacture, and gave complete satisfaction at all times. Each compressed the air to a density of about seven atmospheres, injecting it into an air-chamber, whence, by means of a rigid tube, ending in one of flexible rubber, it was conveyed to the respective drills.