An enthusiastic entomologist baited a sponge with a mixture of malt and honey, and attaching the sponge to a long pole, he held it out of the carriage window of a fast train. The entomologist hope, by knowing the speed of the train, to prove that a certain hover-fly, in pursuing the bait, could sustain a speed of forty-five miles an hour for a distance of three miles. He had some success and he published his findings.
Most of the entomologists' colleagues disputed his claim and were eager to check it. Equipped with bait and time-tables, they themselves embarked on fast train journeys to collect more evidence. Rags soaked in syrup, strips of chocolate-covered netting, pieces of marzipan doused in brandy and imitation flowers dipped in molasses soon lay discarded along the sides of the railway-track, not to mention the walking-sticks, umbrella-handles, sticky flag-poles and fishing-rods. Many of the devices had been snapped of by sharp contact with a telegraphy pole or by a train passing in the opposite direction. One zoologist at a tunnel entrance had lost his head. The tempting bait offered in such abundance, encouraged, by natural selection, the emergence of a hover-fly that could suck glucose at a cruising speed of fifty-file miles an hour over a distance of eight and a half miles, and remember that there were more trains on a Saturday.