HOW THE EARTH IS WEIGHED.

Daily Telegraph (Napier), Issue 3171, 27 August 1881, Page 4

HOW THE EARTH IS WEIGHED.

Mr Drtntnan has given a lecture at the Working men's College, Great Ormondetveefc, " How the Earth is Weiahed and Measured," in which lie observed that one of the greatest triumphs of modern times was the discovery of methods whereby the almost infinitely littla and tho infinitely vast were capable of being measured. Having carefully explained what is meant by specific gravity, the lecturer alluded to the wellknown experiment made on a mountain in Perthshire many years ago, the result of which was to show that when the weight of the mountain was once ascertained, or, in other words, its specific gravity determined, the weight of the globe was found to be 5-6? times as much as the weight of a globe of the same size would be if composed entirely of water. The principal factor in the experiment, the lecturer explained, was a plumb line, the variation of which, between the two sides of the mountain, was proved to be twelve seconds. It was remarkable, however, that the deflection of the plumb line, which was made of silver wire, differed in these tvr.> places, and this was due to the relative positions which occupied towards the zenith. In this way the weight of the earth had been accurately calculated, though what that weight is the lecturer omitted to mention. With regard to the measurement of the earth, the lecturer showed how the apparently intricate problem might easily he solved by calculations ba«ed on the results obtained in regard to the weight of the earth.