148 



THE MINOR PLANETS. 



parts of the earth for observing it : some to Otaheite, some to Cajaneburgh in 

 Swedish Lapland, and elsewhere. The result of their observations proved 

 that the distance of the sun from the earth is ninety-five millions of miles. 



The intervals between the successive transits at each node are 8 and 113 

 years. The following are the series of transits to take place for the next four 

 centuries : 



1874. 

 1882. 

 2004. 

 2012. 



.Dec. 9 4 8 A. M. 



.Dec. 6 4 16 P. M. 



.June 8 8 51 A. M. 



.June 6 1 17 A. M. 



2117 Dec. 11 2 57 A. M. 



2125 Dec. 18 3 9 p. M. 



2247 June 11 21 P. M. 



2255 June 9 4 44 A . M. 



The duration of a transit depends on the part of the sun's disk on which the 

 planet is projected. It may last so long as seven hours, if the planet pass 

 across the centre of the disk of the sun. 



The last transit of Mercury took place on the 7th of November, 1835. It 

 was visible in this country but not in Europe, the sun having set there before 

 its commencement. The next transit will happen in the present year, 1845, 

 on the 8th of May : it will commence at nineteen minutes past four in the 

 afternoon, and will terminate at nine minutes before eleven at night, Green- 

 wich time. At New York it will begin and end four hours and fifty-six min- 

 utes earlier ; it will therefore begin at twenty-three minutes past eleven in the 

 forenoon, and will terminate at five minutes before six in the afternoon. The 

 entire transit will therefore be visible in the United States. 



The transits of Mercury during the present century will be as follows : 



1845 May 8 7 54 P. M. 



1848 Nov. 9 1 38 P. M. 



1S61 Nov. 12 7 20 P. M. 



< 1862 Nov. 5 6 44 A. M. 



187S May 6 6 38 p. M. 



1881 Nov. 8 40 A. M. 



189 1 May 10 2 45 A. M. 



1894 Nov. 10 6 17P.M. 



The times here given are the mean times at Greenwich of the middle of the 

 ( transit. 



MOUNTAINS ON MERCURY AND VENUS. 



It is supposed that mountains of extraordinary elevation prevail both in 

 Mercury and Venus. Those upon Venus are estimated to be about four times > 

 higher than upon the earth. 



Sir William Herschel was unable to distinguish any permanent marks on 

 Mercury. Schroter, however, has been more successful. This astronomer 

 has discovered mountains on the surface of the planet, and has even succeeded 

 in ascertaining the height of some of them. One of them he found to rise to 

 an altitude of 5,600 feet, and another to the scarcely credible height of nearly 

 eleven miles, being nearly four times the height of JElna. or the peak of Ten- 

 eriffe, and more than double the height of the loftiest mountain on the earth. 

 It is remarkable that the highest mountains in Mercury are situated in the 

 southern hemisphere of the planet. 



Schroter, to whose observations we are indebted for much of the knowledge 



