was commenced at Bardonnêche. The badness of the season, however, and {64} the Italian campaign of this year, delayed the rapid progress, and even caused a temporary suspension of this work. The results obtained by the experiments which had previously been made on a small scale at St. Pier d'Arena, failed completely in supplying the data necessary to insure a practical success to the first applications of the new system; numberless modifications, both in the compressing-engines and in the perforating-machines, were found necessary; and several months were consumed in experimenting with, modifying, and improving the huge machinery; so that it was not before the 10th of November, 1860, that five compressors were successfully and satisfactorily at work. On the 12th, however, two of the large conducting-pipes burst, and caused a considerable amount of damage, without causing, however, any loss of life. This accident revealed one or two very serious defects in the manner of working the valves of the engine; and in order to provide against the possibility of future accidents of the same nature, further most extensive modifications were undertaken. By the beginning of January, 1861, the five compressors were again at work; and on the 12th of this month the boring-engine was introduced for the first time into the tunnel. Very little useful result was, however, obtained for a long and anxious period, beyond continually exposing defects and imperfections in the perforators. The pipes conducting the compressed air from the compressing-machines to the gallery gave at first continued trouble and annoyance; soon, however, a very perfect system of joints was established, and this source of difficulty was completely removed. After much labor and patience, and little by little, the perforating-machines became improved and perfected, as is always the case in any perfectly new mechanical contrivance having any great assemblage of parts. Actual practice forced into daylight those numberless little defects which theory only too easily overlooks; but there was no lack of perseverance and ingenuity on the part of the directing engineers; one by one the obstacles were met, encountered, and eventually overcome, and the machines at last arrived at the state of precision and perfection at which they may be seen to-day. About the month of May, 1861, the work was suspended for about a month, in consequence of a derangement in the canal supplying water to the compressors; and it was considered necessary to construct a large reservoir on the flank of the mountain, to act as a deposit for the impurities contained in the water, and which often caused serious inconvenience in the compressors. In the whole of the first year 1861, the number of working days was two hundred and nine, and the advance made was but one hundred and seventy metres (five hundred and fifty feet), or about eighteen inches per day of twenty-four hours, an amount less than might have been done by