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It was Christian Huygens, the famous Dutch philosopher, who applied, in 1658, the pendulum to the clock, and thus led directly to those more refined and subtle improvements, which render our present clocks and watches among the least imperfect of all human contrivances.
The observation made at Cayenne, that a pendulum which beat seconds there, must be shorter than one which beat seconds at Paris, was explained by Huygens, to arise from the diminution of gravity at the equator, and from this fact he inferred the spheroidal form of the earth.
By this means complications were abolished more numerous and perplexing than Galileo himself was aware of, and the problem was reduced to one of simple micrometrical measurement. The "double-star method" was also suggested by James Gregory in 1675, and again by Wallis in 1693; Huygens first, and afterwards Dr. Its advantages were not lost upon Herschel.
This view of the nature of the "imponderables" was in some measure a retrogression, for many seventeenth-century philosophers, notably Hooke and Huygens and Boyle, had held more correct views; but the materialistic conception accorded so well with the eighteenth-century tendencies of thought that only here and there a philosopher like Euler called it in question, until well on towards the close of the century.
Nevertheless, the exorbitantly long tubeless refractors, introduced by Huygens, maintained their reputation until Hadley exhibited to the Royal Society, January 12, 1721, a reflector of six inches aperture, and sixty-two in focal length, which rivalled in performance, and of course indefinitely surpassed in manageability, one of the "aerial" kind of 123 feet.
Accuracy as to time is absolutely essential in astronomy, but until the invention of Huygens's clock there was no precise, nor even approximately precise, means of measuring short intervals. Huygens was one of the first to adapt the micrometer to the telescope a mechanical device on which all the nice determination of minute distances depends.
The former generally goes under the name of its inventor, Ramsden, and the latter is named after great Dutch astronomer, Huygens. The Huygens eyepiece consists of two plano-convex lenses whose focal lengths are in the ratio of three to one. The smaller lens is placed next to the eye.
The resolution of the so-called ansæ, or "handles," into one encircling ring by Huygens in 1655, the discovery by Cassini in 1675 of the division of that ring into two concentric ones, together with Laplace's investigation of the conditions of stability of such a formation, constituted, with some minor observations, the sum of the knowledge obtained, up to the middle of the last century, on the subject of this remarkable formation.
Five only of these were known at the close of the seventeenth century; of which Cussiric discovered four, and Huygens one. It was universally believed that the subject was exhausted. But, on the 28th of August 1780, Herschel's colossal tube revealed to his delighted gaze a satellite nearer to the Saturnian ring than those previously observed.
A Dutchman named Huygens was the first successful inventor of this preparation; and, owing to the adroitness of his work, and of those who followed him and improved his process, one can only detect European lacquer from Chinese by trifling details in the costumes and foliage of decoration, not strictly Oriental in character. With Panels of fine old Laquer and Mountings by Caffieri.
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