Page:Scientific Memoirs, Vol. 2 (1841).djvu/95

Rh Finally, from this value of $$r$$, and from that of $$t$$, determined by observation, may be deduced the value: This number suffices for the comparison of all intensities measured with the same instrument, however the magnetic condition of the apparatus may have varied.

Further, the number $$T$$, which expresses in absolute measure the resulting intensity of the earth's magnetism, may be ascertained by deducing from the observations the value of $$C$$, and multiplying the former number by its square root. $$C$$ is calculated from the observed values of $$a$$, $$b$$, and $$p$$, the mass of the milligramme being taken as the unity of mass: whence $$T$$ is deduced

5. Examination of the result.

This number 1·774, expressing the intensity of terrestrial magnetism on the 18th of January, 1837, possesses, as an absolute measure, the advantage of being directly comparable with the results obtained in 1834 with the magnetometer of the Göttingen magnetic observatory, published in the Göttingen gelehrten Anzeigen of that year. They will be found in part 128, (with the account of the newly-constructed building, and of the instruments, as well as of the first experiments performed there). They are as follow: Two apparatus destined for the same purpose can hardly be more dissimilar than the small apparatus above described, and the magnetometer. It results from the comparison, that the intensity of the terrestrial magnetism in Göttingen has undergone hardly any alteration from 1834 to 1837.

We have also a direct comparison of this number obtained for Göttingen with the result of observations with a third apparatus, differing widely from both the others made at Munich, April 1st, 1836, viz. 1·905, and with the number found for