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65 
Superposed upon physical perceptions much more delicate 
than those of most men. Indeed, a moderate amount of 
scrutiny will detect the growth and development of his 
powers in this respect from year to year. 
Walker tested the same work in a different and more la- 
borious way. He reduced more than a thousand observa- 
tions over the lateral threads in order to compare their 
Tesults with those given by the central one, and with similar 
results. At a meeting of the American Association for the 
Advancement of Science, he publicly stated, that, after an 
extensive series of analogous examinations, made for the pur- 
pose of deciding the relative weight to be assigned to the 
results of different observers, he had found transit-observa- 
tions of only one astronomer, Argelander, which manifested 
€qual precision with those of Gilliss. 
Such were the observations made by Gilliss in the years 
1838 — 42, beginning at the age of twenty-seven, without pre- 
Vious training other than he had given himself, without 
astronomical acquaintances, and, what was more than all, 
Without scientific sympathy until the observations had been 
Prosecuted for more than two years. 
The printed volume contains nearly 700 octavo pages, 
Comprising the detailed observations of each year, with the 
ils of their reduction, the work of each year being spe- 
cially referred to the mean equinox of its commencement; 
and at the close, a General Catalogue of the mean right-as- 
censions of 1,248 stars, formed from these annual tables, — 
together with their precessions, proper motions, and polar dis- 
tances, derived from the British Association Catalogue, and 
Added for convenience in making one of his own results. 
€ come now to one of the noblest achievements of 
: Gilliss’s life, — the construction and equipment of the Naval 
Observatory. To understand the exact bearing and amount 
6* 
