212 HISTOEY OF ASTRONOMY. 



The transit circle was made by Simms, of London. It 

 has a telescope of 30 inches focal length, with an aper- 

 ture of nearly three inches. The circle is 18 inches in 

 diameter, graduated on platina to five minutes ; and it 

 has three reading microscopes, each measuring single 

 seconds. 



The equatorial telescope, made also by Simms, has a 

 focal length of five and a half feet, with an aperture of 

 about 4 inches. The hour circle is 12 inches in diameter, 

 graduated to single minutes, and reads by two verniers 

 to single seconds of time. The declination circle is also 

 12 inches in diameter, graduated to ten minutes, and 

 reads by two verniers to ten seconds of arc. 



The clock was made by Molineux, and has a mercurial 

 pendulum. The instruments were first placed in the ob- 

 servatory September, 1838, and during the whole time 

 of his residence in Ohio, the author pursued a systematic 

 course of observations, as far as his engagements in the 

 college would permit, and without the advantage of an 

 assistant. Among these observations may be mentioned, 

 260 moon culminations for longitude, 69 culminations 

 of Polaris for latitude, 16 occultations, 5 comets, with 

 sufficient accuracy to afford a determination of their 

 orbits, besides a great variety of other objects, for reg- 

 ulating the clock, etc. 



The moon culminations observed at Hudson have been 

 compared with European observations, as far as corre- 

 sponding ones were made, and the following is the result : 

 On 119 nights the moon was observed both at Green- 



