38 



terms : — " I . . . assure you . . . how highly I appreciate your 

 astronomical acquirements, especially your habits of accurate and 

 scrutinizing calculation. I have, on a former occasion, experienced 

 the value of this investigating spirit and laborious industry, in your 

 detection and correction of an error overlooked by myself in the 

 statement sent me from the Royal Observatory, relative to the 

 operations for determining the difference of longitude of Green- 

 wich and Paris in 1825 — a correction which had the effect of 

 raising a result, liable to much doubt from the discordance of the 

 individual day's observations, to the rank of a standard scientific 

 datum ; and thus conferring on a national operation all the import- 

 ance it ought to possess." 



Thus flattering was Mr Henderson's first connection with the Royal 

 Society ; nor was his reception by the Astronomical Society less so. In 

 1828, he prepared an ephemeris for 1829, of theoccultations of Alde- 

 baran by the moon, for ten different observatories in Europe. In 

 return for this and other valuable communications, the Society present- 

 ed him with a copy of their Ti'ansactions, handsomely bound. 



Mr Henderson's reputation as an astronomer was now fully esta- 

 blished, and it was his own wish and the desire of his friends, that he 

 should be placed in a situation more congenial to his favourite pur- 

 suit. Two such situations presently opened; to neither of which, 

 however, was he immediately appointed. The Town-Council of the 

 city of Edinburgh had granted to Mr Short, in 1776, a lease of a 

 portion of ground on the Calton Hill, on the condition tbat an Ob- 

 servatory should be erected on it ; but it was not until about forty 

 years afterwards that any instruments adapted to astronomical pur- 

 poses were placed there, and even then the want of funds prevented 

 it taking its place as an operative establishment. Some yeai's 

 prior to the time of which we speak, a number of gentlemen 

 formed themselves into a society, under the designation of the 

 Edinburgh Astronomical Institution, and by their exertions pro- 

 cured the erection of the present building. Having exhausted 

 their funds, they applied to Government for a grant, which they 

 succeeding in obtaining. From the want of endowment, how- 

 ever, the business of the observatory was somewhat irregularly con- 

 ducted. In 1828, Dr Robert Blair, Professor of Practical As- 

 tronomy in the University of Edinburgh, died. The office had 

 hitherto been a sinecure, and it occurred to many interested in the 

 science, that it might be made useful by the appointment of a per- 

 son qualified to perform the duties of a practical observer ; and that. 



