MoyttP^JhtronomkedSocieiy. '458 



akeady I become familiar with from study and booksv 'Jfhe'instruJ- 

 iments, it is true, were not of first-rate excellence, — a clock an<l 

 transit of 30 inches focal length, with an altitude and azimuth inl- 

 strument by Troughton, formed the equipment of the observatory ; 

 v-T-*but to a young astronomer, who had no other access to astrono- 

 mical apparatus, such an opportunity was invaluable ; and there is 

 little doubt that this circumstance had'coiisiderable induence ou his 

 future history, .h i'-/\ -J- .' rr.in ^niJ -i'i/.v.if ,-n\)u]- iVnv-< 



The opportunity of making observations,' however, did not 'in' any 

 degree withdraw him from the less inviting parts of the science. 

 From the outset of his career he perceived that, in order to be an 

 astronomer, something more is necessary than mere expertness in 

 the use of instruments. He accordingly continued to direct his 

 main attention to the reduction of observations ; and, at an early 

 period, acquired a great knowledge of methods, and great facility in 

 calculating eclipses, occultations, cometary orbits, and, generally, in 

 all the computations and reductions which are subservient to practi- 

 cal astronomy. 



iiiiMr. Henderson first brought himself into notice as an astronomer 

 in 1824, by communicating in that year to Dr. Young, then Secre- 

 tary to the Board of Longitude, a method of computing an observed 

 occultation of a fixed star by the moon, of which that accomplished 

 philosopher thought so highly, that he caused it to be publishedi 

 under the title of an improvement on his own method, in the Nauti- 

 cal Almanac for 1827 and the four following years ; accompanied in 

 some of the last of those years by a second method also proposed by 

 Mr. Henderson. These methods were also published in the London 

 Quarterly Journal of Science ; and he received for them the thanks 

 of the Board of Longitude. About the same time, or shortly after, 

 he began to contribute to the Quarterly Journal of Science various 

 useful papers and notices ; among which may be mentioned, in par- 

 ticular, elements for computing the eclipses of the sun, and lunar 

 occultations of the planets and satellites for the years 1826, 1827, 

 and 1828 ; and lists of the principal lunar occultations for the years 

 1826, 1827, 1828 and 1829. These lists, it is presumed, were the 

 cause of several valuable observations of the phsenomena being made, 

 which, but for them, would probably have been neglected. 



In 1827 he communicated a paper to the Royal Society of London, 

 " On the Difference of Meridians of the Royal Observatories of 

 London and Paris," which is published in the Philosophical Trans- 

 actions for that year, and which furnishes a remarkable instance of 

 the value of that habit of scrutinising calculation for which he was 

 particularly distinguished. In the copy of the observations officially 

 furnished from the Royal Observatory to Sir John Herschel, with a 

 view to his operations in 1825 for determining the difference of lon- 

 gitude between Greenwich and Paris by means of fire signals, there 

 was an error of a second in one of the numbers, which had the effect 

 of causing some irregularity in the results of the different days' work ; 

 but as the discrepancies were small, they had been ascribed to errors 

 of observation. Mr. Henderson, remarking the irregularity, was led. 



