Observations and experiments made at Port Bowen in the years 1824-25, on the figure of the earth, on magnetism, and atmospherical refraction / [Sir William Edward Parry].

  • Parry, William Edward, Sir, 1790-1855
Date:
1826
Catalogue details

Licence: Public Domain Mark

Credit: Observations and experiments made at Port Bowen in the years 1824-25, on the figure of the earth, on magnetism, and atmospherical refraction / [Sir William Edward Parry]. Source: Wellcome Collection.

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    The difference of the results amounts only to 9 ten-thousandths of a vibration in 24 hours. This, it may be observed, is the end and object of the problem ; which, as I have before stated, is strictly a com- parative one ; and the only thing to be insisted upon is, that the same method should be followed, and the same adjustments of the apparatus strictly adhered to, at all the stations which are to be compared together. Supposing, however, that the vibrations recorded in the present experiments, ascertained by the one method, were compared with those determined by the other, the results would differ only 0,14 of a vibration in 24 hours ; a quantity which does not occasion a difference of two ten-thousandths of an inch in the length of the deduced seconds’ pendulum, nor of an unit in the denominator of the fraction expressing the ellipticity. There are cases, of course, dependant on the relative dia- meter of the white disk, to that of the tail-piece of the pendulum, in which a greater or less difference than the above would exist between the two methods so compared ; but this is of no importance whatever, as the object of the problem is fully accomplished by adhering to the same method, whichever it be, at both stations, as before stated. It may not be useless to mention also, that Captain Kater did not adopt the method of disappearances in his comparative expe- riments, until after innumerable trials of other plans, includ- ing that of taking the mean of disappearance and re-appear- ance of the white disk ; all of which he eventually abandoned for that of disappearances alone; and it is certainly to be regretted, that he did not publish an account of these unsuc-