568 Astronomical Society. 



liberality of an English gentleman, whose modesty withholds his name 

 from the public. 



Again, as to hydrography : scientific surveys are gradually spread- 

 ing to every quarter of the globe, under the influence of the noble 

 Lord who has lately enrolled his name in this Society. But little does 

 it matter if coasts are well surveyed, rocks detected, shoals discovered 

 and currents ascertained, if the results are not digested so as to be 

 practically useful to the seaman. It gives me pleasure therefore to 

 announce, that since we last met, an appointment has been made by 

 the Admiralty, which has given universal satisfaction ; for it assures 

 UB, that the day is not far distant, when an Englishman shall visit the 

 hydrographic department of the Dep6t de la Marine of a neighbouring 

 state, without feeling humiliated by the comparative inferiority of the 

 corresponding establishment of his own country. 



Proceed we now to the distribution of our medals. By the minutes 

 read at the table, you have been informed that " one of them has been 

 decreed to Mr. Richardson, for his investigation and determination of 

 the constant of aberration, from observations made at Greenwich with 

 the two mural circles ; — the other to Professor Encke, for his Berlin 

 Ephemeris." 



Three hundred years have now elapsed since Copernicus proposed 

 to the world that system which bears his name ; and if we except the 

 labours of Tycho Brahe, who, besides a catalogue of 800 stars, made 

 attempts to determine the altitude of the pole star at different seasons 

 of the year, little was done by practical observation to support or refute 

 the ideas of Copernicus till the time of Galileo. Observations of the 

 eclipses of Jupiter's satellites induced him to propose them as a means 

 of determining differences of longitude, whilst his discovery of the 

 phases of Venus removed a serious objection to the truth of the 

 Copernican system, and which Copernicus himself predicted would be 

 removed, though he had not the means of doing so himself. About 

 the year 1665, Huygens, by his discovery of the pendulum clock, gave 

 to astronomical observations an accuracy hitherto unknown ; and 

 Cassini, by means of the excellent glasses of Campani, accumulated 

 a vast mass of observations of the eclipses of Jupiter's satellites, and 

 deduced from them tables whereby astronomers could predict their 

 occurrence. 



Notwithstanding the powerful arguments advanced in its favour, 

 the Copernican hypothesis was not generally embraced; for in the 

 year 1669, nearly a century and a half subsequent to its promulga- 

 tion by Copernicus, even the celebrated Hook, to use his own words, 

 *' would not absolutely declare for it*." To settle the matter, there- 

 fore, this extraordinary man, feeling that the instruments of Tycho, 

 although magnificent beyond all others, were, from the nature of their 

 construction, and from their being unprovided with telescopic sights, 

 incompetent to detect minute alterations of sidereal positions, and 



• An attempt to prove the motion of the Earth, from Observations made 

 by Robert Hook, F.K.S., pp. 5 & 7- 



knowing 



