Hax\st. — Address. 39 



was able to oft'er further evidence in confirmation. This statement appeared 

 so important, that Le Verrier went himself to Orgeres, and, after examining 

 most carefully the somewhat primitive modes of Lescarbanlt as to fixing his 

 time and of making his calculations, the great Paris astronomer was convinced 

 of the correctness and importance of the discovery made, and he calculated, 

 from the data given, the approximate elements, of which the following are 

 given in George F. Chambers', F.E.A.S., "Descriptive Astronomy:" — "The 

 inclination of the orbit to the ecliptic, 12° 10' ; daily heliocentric motion, 

 18° 6' ; distance h'orn sun's centre, taking the earth's as unity, 0.143, or 

 about 13,000,000 miles ; period, 19d. 17h." The apx^lication of Kepler's 

 thii'd law, namely — that the squares of the periodic times of the planets are 

 proportional to the cubes of their mean distances, gives a remarkable 

 semblance of truth to Le Verrier's "Elements." On March 20th, 1862, 

 Lummis, in Manchester, observed also what he thought was a planet 

 passing across the sun's disc, but unfortunately he could only continue his 

 observations for twenty minutes, when other duties compeUed him to desist. 



There are also several other instances known where astronomers have 

 observed a small but well-defined round spot pass over the sun's disc, as, for 

 instance, Fritch, October 10, 1802 ; Stark, October 9, 1819 ; Sidebotham, 

 March 12, 1849; Schmidt, October 11, 1847; Decuppis, October 2, 1839; 

 which all have been connected with Lescarbault's planet, and to which the 

 name Vulcan has been provisionally given. The observations of Lummis 

 offered the material to two French astronomers for new calculations of the 

 elements, the results of which are not contradictory to those published 

 by Le Verrier, but appear to confirm them. From the position of the 

 nodes, or those points where the orbit is cut by the ecliptic, it appears that 

 transits over the sun's disc can only be expected between March 25 and 

 April 10 at the descending node, and between September 27 and October 14 

 at the ascending node. However, on October 2, 1876, and at a subsequent 

 meeting, the French Academy received further communications from Le 

 Verrier, in which, with great lucidity, all material at his command was 

 most carefully revised, and the elements of the new planet were given, the 

 existence of which the French astronomer beheves to have been proved. 



Le Verrier shows that many solutions can be given according to the 

 value given to an indeterminate in the formula. Several calculations are 

 then offered which, Avith a possible indeterminate, range from 27.96 to 51,75 

 days (large errors included) for the orbit. The great French astronomer 

 also calculated the time of conjunction in the intervals 1853-63, 1869-77, 

 and 1885-92, and showed that the transits are regulated by a period of 

 about seventeen years. The transit may be expected in the middle of each 

 of those periods, but not for a number of years afterwards, After having 



