The planet Neptune: an exposition and history / By J.P. Nichol.

  • John Pringle Nichol
Date:
1849
Catalogue details

Licence: Public Domain Mark

Credit: The planet Neptune: an exposition and history / By J.P. Nichol. Source: Wellcome Collection.

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    21) of any point to which inquiry is directed, needs skill alone.—This hypothesis of a successful search for an opaque and invisible Jupiter, is not, however, merely an illustrative one;—it is, on the contrary, the equivalent of many investigations, that are far from strange in Astronomy. For instance, we read in works on that science—often indeed to the marvel of those who know not our tech¬ nical proceedings—of the weights of the several Planets ; which are spoken of with as little hesitation as if they had been weighed in our terrestrial balances. Now, these are deduced in this wise: A planet being disturbed by its neighbours, its movements are watched and scru¬ tinized, while the deflecting bodies occupy with respect to it all variety of positions. The effect due to each, is thus separated from the total effect; and from the amount of its influence, the mass or weight of each planet is inferred : nay, speaking more generally, this process of determin¬ ing important physical attributes of these orbs, by inference from their attractive influences, has con¬ stituted the principal branch of physical Astronomy from NewtoiTs time until our own. Shall I dwell, in illustration, on the lights thus obtained regard¬ ing the shape of our own Earth l That body, like