SIMON NEWCOMB, F.R.S., LL.D., D.C.L. xiii 



head of the " Nautical Ahnanac," assisted by a small army of aids 

 and computers, including at least one man of international reputa- 

 tion, and at one time or another a dozen line officers of the navy, 

 this work went steadily forward. 



All who are in any way interested in the professional work of 

 astronomy are familiar with some part at least of the eight quarto 

 volumes of astronomical papers of the " American Ephemeris " 

 which contain the most important results of this undertaking. This 

 is not the place for an analysis of the contents of these volumes or 

 for more than the briefest outline of the work attempted. It may 

 be said that it involved a complete investigation of the orbits of the 

 principal planets, on a uniform plan employing a strictly homoge- 

 neous system of constants derived from practically all existing data. 

 For the latter purpose, the number of observed positions of the sun, 

 Mercury, Venus and Mars alone numbered 62,030, made at thirteen 

 different observatories. The investigations for these inner planets, 

 and the two outer ones, Uranus and Neptune, were made by Profes- 

 sor Newcomb himself or under his personal direction. That of 

 Jupiter and Saturn w^as entrusted entirely to Mr. George W. Hill. 

 A man more competent could not have been found on either side of 

 the Atlantic. Without his valuable assistance, it would hardly have 

 been possible to bring the task to a successful close. Redetermina- 

 tions of the solar parallax, the constants of precession, nutation and 

 abberration were involved directly or indirectly in the undertaking, 

 together with an elaborate investigation of the places of the fixed 

 stars, on which, in the last analysis, all else depends. 



This work, which has been outlined, was near completion when 

 the time for retirement under the age limit arrived. Doubtless, Pro- 

 fessor Newcomb would have preferred to remain at his post some 

 time longer, but the law was inexorable. 



His retirement did not, however, imply cessation from activity. 

 Arrangements were made by which this great work was brought to a 

 practical completion. The lunar researches were provided for by 

 a grant from the Carnegie fund, and were completed only a short 

 time before his death, under conditions of physical suffering, such 

 that very few would have had energy for any purpose. 



