French engineer who built the Mount Cenis (Mount Cenis Tunnel) (Fréjus) Tunnel (tunnels and underground excavations) in the Alps, the world's first important mountain tunnel.

While working at the University of Turin on the construction of a compressed-air ram to supply extra power to locomotives on steep grades, Sommeiller conceived the idea of adapting the machine to rock drilling, for which steam power was not suited because of the difficulty of transmitting it over distances. Commissioned to drive the 7-mile (12-kilometre) tunnel under Mount Cenis, between France and Switzerland, Sommeiller introduced his new drill, which he perfected by trial and error, and a little later, dynamite, just invented by Alfred Nobel. The tunnel was completed in December 1870.