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Germain Sommeiller (15 Mar 1815 - 11 Jul 1871) French-Italian engineer who built the Mount Cenis Fréjus Rail Tunnel (1857-70) through the Alps. To accomplish boring the world's first important mountain tunnel, he introduced the first industrial-scale pneumatics for task. Short biography of Germain Sommeiller >>

Surveying the Mont Cenis Tunnel

How can tunnels meet when bored from two sides of a mountain?

[p.175] Here the question may naturally arise: How can a tunnel, if commenced simultaneously at the sides of a range of mountains, be made to meet in the middle ? It is obvious that to avoid mistake on so vital a matter most careful scientific methods have to be adopted. In the first instance the centre line beneath which the tunnel will run, has, by the aid of a trigonometrical survey of the district to be fixed above ground. In the Mont Cenis work observatories were erected, at some distance from the entrance of the future tunnel, and marks were placed along the line—the accuracy of which was verified astronomically.

The transit instrument set up on Mont Cenis was first directed on the mark opposite to it on the mountains, and shining like a bright star ; its telescope was then tilted downwards until the flame of a lamp set up in the tunnel itself was accurately bisected by the cross hairs. This operation is repeated three more times, the instrument being re-levelled on each occasion, until the mean of the four observations formed what is called a 'series.' A second 'series' is then made by an [p.176] independent observer, and should the mean of the two agree to within a small fraction of an inch, the point denoted by the flame is correctly fixed, and a fresh one is sought for; but if there is much discrepancy in the observations, further 'series' are made until the mean of all the various positions of the lamp warrants the adoption of the point as a station." Such was the accuracy of the methods adopted, first for determining the axis of the tunnel laid out above ground; and, secondly, for transferring this axis underground, that the two tunnels pierced from opposite sides of the Alps, duly met.

Nature bears long with those who wrong her. She is patient under abuse. But when abuse has gone too far, when the time of reckoning finally comes, she is equally slow to be appeased and to turn away her wrath. (1882) -- Nathaniel Egleston, who was writing then about deforestation, but speaks equally well about the danger of climate change today.

Carl Sagan: In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion. (1987) ...(more by Sagan)

Albert Einstein: I used to wonder how it comes about that the electron is negative. Negative-positive—these are perfectly symmetric in physics. There is no reason whatever to prefer one to the other. Then why is the electron negative? I thought about this for a long time and at last all I could think was “It won the fight!” ...(more by Einstein)

Richard Feynman: It is the facts that matter, not the proofs. Physics can progress without the proofs, but we can't go on without the facts ... if the facts are right, then the proofs are a matter of playing around with the algebra correctly. ...(more by Feynman)

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