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and changing sign in passing into the southern hemisphere. This 

 experiment, as is well known, had actually been carried out by 

 M. Foucault, and has since been repeated by numbers of others. 



More recently still, M. Foucault has invented another instrument, 

 which he calls a gyroscope, for the experimental demonstration of 

 the earth's rotation. The action of the instrument depends on the 

 fixity of the plane of rotation of a disk made to revolve with great 

 rapidity about its axis. The instrument is quite small, and may be 

 used on a table, but requires great nicety of construction. By 

 availing himself of the precessional motion of the axis when the disk 

 is acted on by a force tending to turn it about an equatorial axis, 

 M. Foucault is able, in consequence of the construction of the instru- 

 ment, not only to exhibit the earth's rotation, but also to determine 

 experimentally the plane of the meridian and the latitude of the 

 place. 



M. FOUCAULT, 



I present to you this Medal in testimony of our admiration of 

 the skill, ingenuity, and talent displayed in your very remarkable 

 experimental researches. 



Your Council have awarded one of the Royal Medals for this year 

 to Mr. John Russell Hind, Superintendent of the Nautical Almanac, 

 for his researches and discoveries in Astronomy ; an award, which I 

 feel sure will meet the warm concurrence of the Society. 



Mr. Hind commenced his astronomical labours as assistant to the 

 Astronomer Royal, to which office he was appointed in November 

 1840. 



Mr. Hind held that situation during four years, and was distin- 

 guished by his punctuality, attention and zeal; moreover, he devoted 

 his leisure hours to the careful reading up of astronomy, both 

 practical and theoretical ; thereby familiarizing himself with the 

 various methods of observation and reduction, as well as the calculation 

 of orbits for comets and double stars. His first attempt at positive 

 computation was an ephemeris of Bremicker's comet for 1840, which 

 Mr. Airy printed in the Greenwich Observations of that year. In 

 1844, on being applied to by Mr. George Bishop, a Fellow of this 



