Thus, however far the consequences of Lobachevski's hypotheses are pushed, they will never lead to a contradiction.

Lobachevski has proved not, by creating non-Euclidean geometry.

If Lobachevski's geometry is true, the parallax of a very distant star will be finite; if Riemann's is true, it will be negative.

What victory heralded the great rocket for which young Lobachevski, the widow's son, was cast into prison?

If this were so, experience would be capable of deciding between the hypothesis of Euclid and that of Lobachevski.