316 A brief Memoir of the late Walter Folger. 
In concert with several observers on the continent, among 
whom were Bowditch and Jefferson, he made special preparation, 
to observe the beginning and end of the solar eclipse of 1806, 
total in Boston and nearly so at Nantucket. 'The day was cloud- 
less and the results satisfactory. 
Probably the most valuable observations that he ever made 
were those on the comet of 1807—the first comet he had ever 
seen. On the first appearance of this body, he commenced tak- 
ing a series of angular distances to the various fixed stars near 
which it passed. Then angles were taken with a sextant, in the 
use of which he was very skillful. Having been in the habit for 
many years of adjusting this instrument for the seamen of his na- 
tive town, no one could use it more dexterously. His application 
to this work, as to every undertaking, was unremitting; he fol- 
lowed it through the whole period of its visibility, and in the lat- 
ter part of autumn, while the comet was circumpolar, by obtain- 
ing angles through the whole night above and below the pole, he 
was able to detect its parallax, as well as its motion and position. 
These observations were never published, and it now may 
well doubted whether a vestige of his notes remain, the labor 
having been performed chiefly for his own gratification. ‘The 
great comet of 1811 did not escape his attention, and his observa- 
tions met with a better fate. He was induced to publish them 
in detail, and they were so numerous that the angles alone, when 
reduced, occupied an entire page of a Boston newspaper. With 
his expertness in the use of the sextaut, and the sharp nucleus of 
that beautiful comet, his results were exceedingly accurate, and 
were so esteemed by Dr. Bowditch who used them in calculating 
its elements. 
In earlier life he had constructed a number of small telescopes ; 
but at the age of fifty-four he undertook the construction of a re- 
flector of considerable size, and finished it in the succeeding year. 
This telescope is a Gregorian, the larger speculum is five inches, 
and the smaller, one inch in diameter. Its focal length is five 
feet, with one eye-piece magnifying not less than three hundred. 
It is not mounted equatorially, nor has it any arrangement for’ 
measures; but it is furnished with rack work for slow azimuth and 
altitude movement. The stand is of oak and has four legs on the 
plan recommended by the elder Tulley, and it is exceedingly 
steady— illustrating the advantage of this method for firmness no 
less than safety. ‘The tube is of sheet iron and very neatly fin- 
ished. The stand, which was made by his son, is the only part 
which was not formed by his own hands. In grinding the large 
speculum he dispensed entirely with the bed of hones, using the 
grinding powder after it was worn very fine on the pewter tool. 
In reference to its figure, there is doubt whether its curve is pat- 
abolic. He objected to that form and demonstrated that it is not 
