During 29 February 1880, it was announced that both of the tunnel's advance borings had broken through into one another around the mountain's middle point. It was also observed that a high degree of accuracy had successfully been achieved, a testament to the stringent surveying and directing that had been performed throughout the construction phase. The occasion was widely publicised and hailed as a major engineering triumph; the engineer Adolphe Gautier described it at the time as being "the greatest work hitherto attempted by man".