HISTOEY OF PHYSICAL ASTBONOMY.

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by agreement, meet weekly in London on a certain day to treat of suchmatters. Among the individuals who thus used to assemble together,were Wilkins, Goddard, Wallis, and Samuel Foster, Professor of Astro-nomy in Gresham College . In 1648-9 the attendance at the weeklymeetings was considerably reduced by the removal of several members toOxford, who established a similar association in that city. The originalminutes of the Oxford Philosophical Society, dated the 33rd of October,1651, are still preserved in the Ashmolean Museum of that city. Theembryo Society of London still continued to hold its meetings, but itseems to have fallen into a very languishing condition until the year1660, when the restoration of Charles II. , by holding out the prospect offuture tranquillity, had the effect of infusing renewed vigour into its pro-ceedings. The earliest official document of the Society is dated Novem-ber 28, 1660. It was finally incorporated by Royal Charter on the 15thof July, 1662. The first President was Lord Brouncker, one of the mosteminent mathematicians of the age. Among those members who took anactive part in promoting the objects of the Society at this period, may bementioned the President Lord Brouncker, Boyle, Wilkins, Wren, and SirRobert Moray. A few years after the establishment of the Royal Society upon a permanent basis, a similar association was formed at Paris underthe designation of the Royal Academy of Sciences . The first meeting ofthis celebrated body was held on the 22nd of December, 1666. Some ofthe earlier members were Roberval, Auzout, Picard, and Richer. A fewyears later, it was enriched by the accession of Huyghens , Roerner, andCassini, who were enrolled as members.

Numerous institutions for promoting the cultivation of science havebeen established in the different countries of Europe at a later period thanthat above referred to; but it is no depreciation of the well-earned repu-tation of many of them to assert that, at no epoch of their history havethey in any instance exercised an influence so unequivocally beneficial asthat exercised by the Royal Society of London, and the Academy ofSciences of Paris , during the early period of their existence. It is to beborne in mind that the last-mentioned institutions were founded at a timewhen the inductive philosophy was still engaged in mortal conflict withthe scholastic system of Aristotle , and when, consequently, an organizedunion of the scattered energies of its adherents could not fail to accelerateits final triumph. Practical astronomy participated largely in the advan-tages derived from these institutions. New improvements, both in theconstruction of instruments and in the methods of observation, were dis-seminated throughout Europe with a rapidity hitherto unknown, andthereby facilitated in a vast degree the attainment of still further excel-lence.

The invention of the micrometer was one of the earliest of those im-provements which in the seventeenth century had the effect of establishingthe methods of astronomical observation upon a totally new basis. Themeasurement of small angles was found by astronomers, in all ages, to beone of the most difficult objects connected with the practice of observation.Archimedes , in an attempt to determine the apparent magnitude of thesun, was unable to arrive at a result of greater precision than that theapparent diameter was greater than 27', and less than 32'. Coming downto modern times, we have seen that Tycho Brahe was so misled by hismeasurements of the apparent diameters of the sun and moon, as to cometo the conclusion that a total eclipse of the sun was impossible. Indeed it is

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