lf, as we believe we shall presently show, a longer mile were in popular use, it may be doubted whether the authors above alluded to were aware of the difference. They certainly did not perpetuate such knowledge; for Dr. Bernard, the most profound of English metrlogists, found the mile of 5000 feet sufficiently common in old writings to induce him to give it a name, and call it the English geometrical mile, meaning, we suppose, that principally used in mathe matical writings; but he does not give the least hint that any other mile, except this geometrical mile and the statute mile, was ever in existence. Nor does his predecessor (heaves, when he remarks that great differences have been observed between measured and statute miles, hint at such discordances being derived from the remains of any old and different measure, or at any acknowledged measure different from the statute mile. This mile of 5000 feet continued in use among seamen, whose {measures depend more upon writers on navigation than on acts of parliament, until the earth's dimensions became better known. A very old notion as to the earth's magnitude gave 60, or at most 62i, Roman miles to the degree. The sea mile tallied with that of writers on shore, until the measures of Picard, &c., became well known ; but the sixtieth part of a degree of latitude is so convenient a standard measure for the sailor, that under the name of a nautical or geographical mile it has lengthenenecl with the common estimation of the degree of latitude. Thus, in the time of Gunter we find the degree described as 60 miles of 5000 feet each; though ho certainly says (Os the Cross-Staffe, b. xi., cap. 6), that by comparison of observations,' ho thinks 352,000 feet nearer tho truth. Even almost as late as the Revolution some common works written for landsmen describe the sea league as three Italian miles, which answers nearly to 15,000 feet. Ily the time of 1)r. Bernard however we find the sea halo described as coinciding with the statute mile (De 211cns. et Pond., p. 202) ; but this is in a work of science and authority : and Oughtred (before the date of Bernard's book) says that it is " taken (Or rather mistaken) that 60 statute, miles make a degree." It is most likely that the sea league would in the first instance be taken from the com mon league; and certainly 15,000 feet, or 2.84 statute miles, is almost the same as the length which different deduction, will give for the old land league.
We now proceed to the main question, the length of the old English mile : premising that the utmost we can attempt is a clear proof that the old popular mile differed considerably from the modern mile. The gradual changes of this old mile ( which the general history of iti nerary measures may lead us to suspect) must be traced out by closer Investigation of antiquarian authorities than mathematicians have been wont to make, and better estimation of their relative values in a mathematical point of view than antiquaries have hitherto been capable of making.
There is a tradition among antiquaries (Sir II. Preface to Domesday ') that this old mile was somewhere about a statute mile raid *-halt. This tradition is not to be relied on ; for though In all probability it agrees with the truth, yet it may have arisen from another circumstance. We have more than once heard it proved by the emersion that, even within the memory of man, distances were measured in the remote parts of the country by a longer than the statute mile ; for instance, that York was said to be 150 miles from London, while it is really more than 199 statute miles. This is per fectly true; but the reason is perhaps different from that given, as the following account will show : The first actual measurement of the roads in England. in statute miles, was made by John Ogilby, cosmographer to Charles IL. and was published by him in 1675, under the title of 'Britannia,' with copious descriptions, and 100 copper-plates of the roads, in a large folio volume : the instrument used was called by him a tched-dimensurator, by others, a roay-wiser, and answers entirely to the perambulator now in use. Various editions of this work wero published, of which we
have seen three, and D'Anville mentions a fourth. It is worth noting that this measurement, as compared with older ones, soon same into general use : thus in a little work for men of business, called The Cempleto Tradesman, or Exact Dealer's Daily Companion, London, 16S4, we, find a list of Ogilby's distances from town to town, compared with those formerly adopted. The latter were called by Ogilby cont ,puted miles, and the meaning of this word might be doubted, but it is proved to mean miles in common use by previous publications. Thus in Samuel lilorland's Description and Use of Two Arithmetic Instru ments,' &c., 1673 (or two years before Ogilby's publication), we find the distances called " computed " by Ogilby set down as tho (supposed) real distances. D'Anville appears to have seen an edition of Ogilby (of which there is one at least) in which the word computed is always contracted into corn. This lie supposed to mean common, and the whole of his chapter on English itinerary measures (' Waimea hind mires,' cap. x.) must in consequence be read cautiously, as he assumes to be indisputable that there was a common mile in use at the Revolution, which was about a quarter longer than the statute mile. But on the authority of the silence of Bernard and Greaves above referred to, we must remain of a different opinion, and must suppose that the computed miles preserved by Ogilby had been intended to represent the number of statute miles, but erro neously given.
What then may these computed miles mean, which had served the common purpose in the estimation of distances! The word computed never meant reputed, but was always applied to a result of reckoning of seine kind or other. Ogilby says, "Whence these computations arose is altogether uncertain; the nearest conjecture is, that they seem to exclude the whole length of the towns, and to be the distance from the end of one town to the beginning of the next, not regarding the fractional parts of a mile, but taking the lesser integer." The com puted miles always give a smaller figure than the measured ones, or the same, never a greater; and a little examination will render it difficult to suppose that the preceding explanation can be the true one. For independently of its having been the known practice to measure the roads from a conspicuous part of every town, the preceding will not explain differences of four, five, and even seven miles in a stage of less than thirty ; neither will it explain long stages being oftcu of the same number of computed as of measured miles. Our own conviction is that the computed miles are nothing more than distances measured on a map in a straight line from town to town, which differ from those measured on the roads more or less, according to the deviations and curvatures of the roads. Should this opinion be correct, we might expect beforehand, first, that the roads in the 'neighbourhood of the metropolis would appear more direct than the general average; secondly, that the principal roads would show indications of being more straight than the average deduced from all classes, and from cross as well as direct roads. Beth these things appear in the general results, and we can clear ourselves of the suspicion of bias in our selection of instances by throwing that task on others. In the first place the roads near London agree so much better in the computation, so called, and the ineasurement, that both Ogilby and D'Anville notice the circum stance, and conclude that a shorter mile was in use in the neighbour hood of the great city. We find on examination that such is the case with most of the twenty-mile distances about London, which yield about 120 measured miles for 100 computed miles ; and this happens particularly with those routes which come earliest in Ogilby's work ; but 120 would have been increased almost up to the general average by taking twenty miles on every road out of London.