observation, and as though he had seen nothing worthy of notice. When the surveyors had completed their proofs Mr. Bidder, who had carried on in his own mind a calculation of the heights noted in all the books, not merely of the salient points upon which the witnesses had been examined, but also of the intermediate rises and falls noted in the several books, suddenly exclaimed that he would demonstrate to the Committee that the section was wrong. He then went rapidly through a calculation which took all by surprise, and clearly proved that if the levels were as represented at one point they could not possibly be as represented at another and distant point. The result was that the errors in the levels were reported, and
the Bill was not allowed to proceed."[1]Some of his extraordinary achievements have been reported, but they are somewhat doubtful. It will be best to quote only one that is well authenticated from the Proceedings of the Institute of Civil Engineers (lvii. 309).
"On 26 September, 1878, being in his 73rd year, he was conversing with a mathematical friend on the subject of Light, when, it having been remarked that '36,918 pulses or waves of light, which only occupy 1 inch in length, are requisite to give the impression of red,' the friend 'suggested the query that, taking the velocity of light at 190,000 miles per second, how many of its waves must strike the eye and be registered in one second to give the colour red, and, producing a pencil, he was about to calculate the result, when Mr. Bidder said, 'You need not work it; the number of vibrations will be 444,433,651,200,00'"
- ↑ Obituary Notice in Transactions of the Devonshire Association, 1879. See also that for 1886, pp. 309-15.
