The question, “How far to Holyhead?” had in old days been a difficult one to answer. It was not only in the uncertainty and variety of routes that the difficulty of accurately measuring the number of miles lay, but in the wild and conflicting ideas as to what really constituted a mile. This uncertainty lasted until the middle of the eighteenth century, when the first milestones since the days of the Romans were erected. It was, in fact, not before 1750, when, as part of their statutory obligations, the numerous Turnpike Trusts began to erect their milestones, that distances began to be publicly and correctly measured. It had already long been known that the mileages computed by the Post Office, in dealing with postmasters and the mails, were very inaccurate throughout the country, and for many years previously compilers of road-books had been accustomed to print two tables of distances; one the “computed” and Post Office mile, and the other the measured mile.

The first of English makers of road-books, John Ogilby, mentioned this discrepancy, so early as 1675, when he published his great work, Britannia. Ogilby who had been commissioned by Charles II. to survey the roads and measure them, did his work thoroughly. He claims to have travelled 40,000 miles in compiling his book, a folio volume of great typographical beauty and exquisitely engraved plans of the roads. In making his survey, he used what he calls a “wheel dimensurator.” Exactly what this was is shown in the beautifully etched title-page by Hollar, to his first edition, where Ogilby himself is seen on horseback, directing the course of two men; one wheeling the instrument, the other checking its measurements. It apparently was a wheel fitted with a handle and wound with a ten-mile length of tape. Trundled along, it unwound the tape, the intermediate distances being noted down by the assistant. Ogilby very soon discovered that although the Post Office gave the mileage to Birmingham and Holyhead respectively as 89 and 208 miles, it was then really 116 and 269 miles. The Post Office mile, which he calls the “vulgar computation,” was therefore practically a third larger than our so-called Statute Mile, dating from 1593 and constituted by a statute of the 35th year of Queen Elizabeth’s reign, not so much for the purpose of creating a standard of measurement for the kingdom, as for defining certain limits. That Statute was passed by a Legislature dismayed by the rapid growth of London, and was an enactment forbidding persons to build within three miles of the capital. When it came to the point of defining a mile, it was found that no such measure had ever been officially fixed, and that English, Irish, Scottish, and local miles were of variable lengths. The mile was then taken to be eight “forty-longs,” or furlongs, of forty perches each; a perch to consist of 5½ yards.

That this extraordinary difference between actual distances and those computed by the Post Office should have arisen on all roads is inexplicable, and that it should have remained after Ogilby’s official measurements had proved the “computed” miles utterly wrong is an astonishing proof of the vitality of error. But the real trouble arose with the appearance of milestones along the turnpike roads. They were the cause of much bitterness and contention between postmasters and the Post Office, and between keepers of posting-houses and travellers.

Those who did business for the Post Office claimed extra mileage, and travellers posting to or from Birmingham and Holyhead found themselves charged in the aggregate for 27 or 62 miles extra, as the case might be; which, say at 1s. 3d. a mile for chaise and four horses, was a consideration. Travellers resented this difference and pointed out that, if posting establishments could always have afforded to do certain stages at certain prices, they could continue so to do; to which those men of horses and carriages replied by pointing out that the milestones were official and that they themselves paid more carriage duty on the extra mileage; a generally conclusive retort.