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A brief Memoir of the late Walter Folger. 317 
the best except for objects whose distance is infinite. When the 
specula were finished, they were placed for trial in a rude tube of 
deal board mounted on a temporary support and directed to the 
planet Jupiter; and whatever may have been its subsequent per- 
formances, which were certainly no better than what might have 
been anticipated,—in this first trial its performance was astonish- 
ing. For light, distinctness of vision, and clearness of outline, it 
is scarcely surpassed by the larger and far more expensive instru- 
ments of the present day. While in this tube and with this tem- 
porary adjustment, he viewed the moon under favorable circum- 
Stances of weather, three days after the change, and detected that 
delicate thread of corpuscular light which was seen by Schréter 
in the early part of the year 1792 with a reflector of nearly the 
same size, and he described it almost in the words of the German 
astronomer, though he had never seen the paper of Schréter and 
knew nothing of the discovery. When the telescope was com- 
pleted and mounted, his neighbors thronged his house to obtain 
a sight of the moon or other celestial objects, and although a se- 
vere tax upon him, he at all times gratified their wishes with the 
most enduring patience. 
a the occasion of the return of the Encke comet in 1829, 
when the theory of Encke was so strikingly verified, he became 
interested in the subject of a resisting medium, and for his own 
Satisfaction constructed a set of tables for the determination of the 
place of the comet for any period past or future within the limit 
of a thousand years. ‘The labor in the construction of these ta- 
bles was immense ; but with his usual untiring zeal and applica- 
tion, he accomplished it, before the comet was beyond the reach 
of the telescope. The figures made in this work were so numer- 
ous that he often exhibited the sheets containing the rough com- 
putations asa curiosity. ‘These tables he always declined pub- 
lishing though often solicited to do so, and they remain to t 
y among the fragments of his industry. a 
He kept for many years a meteorological journal, using a ba- 
rometer and thermometer of his own construction, both o which 
were remarkable for their accuracy. Indeed he was never satis- 
fied with the use of any instruments unless he was entirely confi- 
dent of their utmost aceuracy, and to be certain of this, he was 
compelled to form them with his own hand. In the prosecution 
of his meteorological inquiries he convinced himself of the truth 
of the gyratory theory of d and defended it with energy. 
In the more vigorous period of his life, he was a contributor to the 
mathematical periodicals of the day, solving the more difficult 
problems and proposing others. Among his correspondents in 
Science, were Doctors Bowditch, Prince aud Oliver, and President 
elferson. 
