Opinions derived from long experience are exceedingly valuable, and outweigh all others, while they are consistent with facts and with each other; but they are worse than useless when they lead, as in this instance, to directly opposite opinions.

Peter Barlow (1835). Second report addressed to the directors and proprietors of the London and Birmingham Railway company, founded on an inspection of, and experiments made on the Liverpool and Manchester railway. B. Fellowes. p. 4.