44 P7TMR. BARLOW'S ACCOUNT OF THE CONSTRUCTION OF 



of accuracy ; and it will not of course be understood that I am now speaking 

 of extreme astronomical accuracy. 



I found, however, the action so complete, that I determined to try how far it 

 could be useful in this way. The lower curb was therefore carefully divided 

 by hand into degrees and quarters, the meridian obtained by the best means 

 in my power, an index fixed to the bottom of the frame and adjusted to the 

 zero of the circle. A graduated circle, not seen in the plate, was then attached 

 to the bearing frame with a suspended plummet, the telescope put upon a 

 meridian star whose altitude was known, and the arc adjusted accordingly. 

 With these apparently rough means, and another for converting right ascen- 

 sion and declination into azimuth and altitude ; and with the help of an ex- 

 cellent pocket chronometer by Messrs. Parkinson and Frodsham, my son, 

 who has acquired great dexterity in the use of the instrument, can at any 

 time select the right ascension and declination of the star from the catalogue, 

 convert these into azimuth and altitude, direct the instrument towards the 

 object, and be seated quite at his ease observing, in three minutes. 



In a bright night, — and for observing a known star this is of course unneces- 

 sary ; but for less conspicuous stars, which are scarcely distinguishable except 

 by their catalogue positions, as also for finding any star before daylight is quite 

 gone, or a planet in the day-time, these means, although far short of those 

 aflforded by an accurate equatorial, are very serviceable. 



It should be observed that the stand was originally designed to work from 

 the horizon to the zenith, which it is capable of doing ; but I have limited its 

 present action to an altitude of 65°, this being the greatest height I can obtain 

 without cutting the upper curb of my observatory roof, which I am rather un- 

 willing to do, for obtaining what is at best, with such an instrument, a very in- 

 convenient position for observation. 



Description of the Observatory. 



It has been already stated that this room is circular, having a clear diameter 

 of 16 feet. It is constructed as follows : A foundation wall 4 feet deep of 14-inch 

 brickwork is first laid, and on this is imbedded a circular wooden curb in two 

 thicknesses, each 2 inches deep and 4 broad, properly united with bolts, screws, 

 and keys. Another exactly similar curb, united in the same way, forms the 



