TIMING THE TRAIN – AND CHECKING THE RECORDS
This exchange between Sherlock Holmes and Dr. Watson is so well known as to not require to be referenced: “We are going very well,” he [Holmes] said, looking out of the window and glancing at his watch. “Our rate at present is fifty-three and a half miles an hour.” “I have not observed the quarter mile posts,” said I. “Nor have I, but the telegraph posts upon this line are sixty yards apart and the calculation is a simple one.”1
Since Holmes and Watson are on their way to Dartmoor to investigate the mystery of the disappearance of the racehorse ‘Silver Blaze’, we can only assume that he is travelling on the Great Western Railway from Paddington via Bristol to Exeter in 1892; is it too much to hope that his train is hauled by one of the last broad gauge locomotives, perhaps Great Western itself? I set my nephew, who is an engineering undergraduate and who loves mathematics and physics, the task of writing down Holmes’s working (which incidentally, he obviously does in his head). His response is worth sharing in full: “… an interesting puzzle, made more so because I always use SI units, I had to Google how many yards were in a mile. [!] The best solution that I can come up with is this:
3,600 seconds in a hour
1,760 yards in a mile
Therefore 1 yard per second [yd/s] = 2.045mph
53mph = 25.91yd/s
53.5mph = 26.16yd/s
54mph = 26.41yd/s
Rounding to 26yd/s
60/26 = 2.3
Therefore the time elapsed between 11 posts (10 x 60 yards) = 23 seconds
600 yards in 23 seconds is 53.36mph.
“There are of course many ways of doing this; the first thing I tried was 53.5x1,760)/3,600 = 26.15yd/s but the book says a simple calculation. I’ll be honest, I did a little Google search and the first thing that came up was someone theorising that Sherlock was bluffing. So I think this is about as close as you can get.”2
Formal recording of a train’s performance goes back more than 150 years, but it was probably the ‘Railway Race to the North’ in 1888 that first made it popular, so that by the end of that century it was pretty generally accepted by engineers and railway managers as one of the means by which the success of any design was authenticated. I suspect no reader of this magazine needs to be reminded of the long series of articles that appeared in the Railway Magazine, successively from September 1901, in which Charles Rous Marten and then R. E. Charlewood, Rev. W. J. Scott, J. F. Gairns and from 1909 until 1959 Cecil J. Allen, using their own or the logs supplied to them by outsiders, recorded and commented exhaustively upon train performance. In later years similar records appeared in most of the Ian Allan magazines and, indeed, in others.
My first attempt, as a young boy, in the summer of 1958 was to record the 19.00 from Weston-super-Mare as far as Didcot, using my father’s watch, which I had to ask him to show me when we stopped, and on one occasion that of an RAF man sitting opposite me. Needless to say the resulting
