i66 



EECEEATIVE SCIENCE. 



to which, can he put into the coat-pocket, 

 and the stand into a small carpet-bag. The 

 main principle is the same in both. 



To describe the latter is the object of 

 this paper. The design of the former class 

 of iiistrument is to ascertain, with great pre- 

 cision, the place of any celestial object, for 

 purposes which it would not accord with the 



ascension of the comet is so many hours, mi- 

 nutes, and seconds, and the declination north 

 or south, or the folar distance (which can 

 be converted into declination, and vice versa), 

 is so many degrees, minutes, and seconds of 

 arc. By a simple calculation, with the aid 

 of the Almanac, the observer knows when 

 the comet will be on the meridian; and 



intention of this paper to explain ; the design 

 of the latter is simply iofind an object in the 

 heavens (without having to fish for it), this 

 being done by the setting of the circles 

 attached thereto by means of moderately 

 well-divided graduations. 



Suppose a comet to appear. The owner 

 of such an instrument reads in the public 

 prints that at such and such a time the right 



hence, at any hour before or after that time, 

 he knows how far in hours, minutes, and 

 seconds of time, or degrees, minutes, and 

 seconds of arc, it is from the meridian. The 

 error of his watch or clock having previously 

 been ascertained within a fraction of a mi- 

 nute, a nicety sufficient for the purpose in 

 view, he proceeds to set the telescope, by 

 means of the graduated circles, to a given 



