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the Duke of Marlborough, from a series of observations made with the best instruments, the intersection of this parallel with the meridian could be fixed with accuracy, and gave of course another subdivision, both of the geodetical distance and the celestial arch. The same was done with respect to the parallel of Greenwich; and thus, besides the total length of the meridian line from Dunnose to Clifton, there were given three intermediate points in that line, with the distances between them, and also the amplitudes of the corresponding arches in the heavens. From the comparison of all these determinations, some curious and unexpected conclusions have been deduced.
1. The entire length of the meridian line, from Dunnose to Clifton, is 1036337 feet, or 196.29 miles; the latitude of Dunnose being 50° 37′ 8".21, and the arch between its zenith and that of Clifton 2° 50′ 23′′.38. Hence, the length of a degree in the middle between these places, or in lat. 52° 2′ 20′′, is 60820 fathoms.
2. In the same way, by computing the length of a degree for the middle latitude between ArdburyHill and Dunnose, viz. 51° 35′ 18′′, it is found equal to 60864 fathoms. This is 44 fathoms greater than the former, though, being about 27′ more to the south, it ought, according to every notion of the earth's oblate figure, to be several fathoms less.
3. Comparing, in like manner, the distance between Ardbury-Hill and Clifton with the arch intercepted by their zeniths, the degree in the latitude of 52° 50′ 30′′ is 60766 fathoms ; which is less than either of the former, though, by being a good deal further to the north, it ought to be considerably greater.
4. The intersections of the parallels of Blenheim and Greenwich with this meridian, give results of the same kind, all tending to show that the degrees diminish on going from the south to the north, though not regularly, nor according to any law yet known. These inconsistencies are very striking, when it is considered that, on the supposition of the earth being compressed at the poles, the degrees of the meridian must go on increasing as we proceed northward, and in our latitudes nearly at a uniform rate; each degree exceeding that immediately to the south of it by about twenty fathoms, according to the theories that make the earth's oblateness the greatest; and about ten, according to those which make it the least.
To whatever cause these irregularities are to be attributed, it cannot be, we are well convinced, to the inaccuracy of the observations. The probable limits of such inaccuracy are considered by Major Mudge himself; and though he estimates them as very small, yet, by any one who has carefully studied the observations themselves, and remarked
their closeness to one another, he will not be thought to have diminished them more than the circumstances authorized him to do.
He states it as his opinion, after a re-examination of all his data, that the extreme of the error in the measurement of the whole distance, though nearly 197 miles, is not more than 100 feet, answering to about 1" of a degree, and that the probable error does not exceed one half of that quantity. In the determination of the celestial arch he does not state so precisely his estimation of the error, or the limits within which it is contained; but, taking in the multitude and the agreement of the observations, we should imagine that at any one station it can hardly amount to a second. It is therefore to the action of some external cause, affecting the direction of the plumb-line, that the irregularities above stated are to be ascribed. "I am disposed," says the Major, "to believe that the plumb-line
was drawn towards the south, from the action of matter both at the northern extremity of the arch and at Ardbury-hill; but more particularly at the first-mentioned station."-" The general tenor of the observations seems to prove that the plumb-line of the sector has been drawn toward the south at all the stations, and that by attractive forces, which increase as we proceed northward." From what physical cause this attraction proceeds,-from what circumstance in the structure or formation of the
island, he does not offer any conjecture, neither shall we presume to do so. The continuation of the meridian to the north will probably throw some further light on this interesting subject.
It is, however, material to be observed, that when the degrees are irregular, as they appear to be here, the magnitude of the middle degree between two given latitudes is not rightly found, by dividing the terrestrial distance by the celestial arch. This process is only correct, on the supposition that the degrees increase or decrease in arithmetical progression, or at an uniform rate: if they vary according to any other law whatever, the degree found by the above operation will not be the degree in the middle point of the arch. This caution is necessary to be attended to, if we would deduce from the observations no more than what necessarily follows from them. It may be further remarked, that in the doubt we are in about the figure of the earth, whether it be a solid of revolution, and whether different meridians may not be unequal and dissimilar curves, it may be questioned whether the places on one meridian can be safely reduced to another, by the supposed intersections of their parallels with this last; and whether, by supposing such reduction, as when the observatories of Greenwich and Blenheim are placed on the meridian of Dunnose, we do not complicate the question unnecessarily by the introduction of a new and unknown
element. The distances of these places to the eastward of the meridian being but small, it is indeed probable that, in the present case, any error introduced by them must be very inconsiderable; but it is at least right to be apprised of the possibility of its existence.
Though we have no doubt that irregularities, which are at present so difficult to be accounted for, will, by the prosecution of the subject, become perfectly explained, we confess that we have felt some disappointment on reflecting, that hitherto the more that has been done to ascertain the figure of the earth by the measurement of degrees, the less satisfactory in some respects, has our knowledge of it become. The more microscopically we have observed, the more irregularities we have discovered; and in the last experiment, which may be justly reckoned the best, what is accounted the natural order of things, has been almost completely inverted. All this, however, is only a motive for continuing the research; which, if prosecuted with skill and perseverance, must ultimately lead to the knowledge of the truth. The time was, when the planetary motions were involv ed in the same confusion, and seemed the more unaccountable and perplexed, the more carefully they were studied. We may hope for the same issue in both cases, and that the figure of the earth