608 PHILOSOPHICAL TRANSACTIONS. [aNNO 17Q5. 



tern to my indefatigable assistant, Carolina Herschel, who brought all the Bri- 

 tish catalogue into zones of 1° each, from the 45th degree of north polar dis- 

 tance down to the horizon, and reduced the right ascension of the stars in it to 

 time, in order to facilitate observations by the clock. This catalogue was after- 

 wards completed from the same degree up to the pole in zones of 5" each ; and 

 the variation in right ascension from 1° of change in longitude, was also reduced 

 to time, for every star in the catalogue. To this were added computed tables 

 for carrying back present observations to the time of that catalogue ; which 

 method I preferred to bringing the stars it contains forward to the present time, 

 on account of conforming with the construction of the Atlas Coelestis, which 

 was of great service. 



The evident use of such a catalogue must undoubtedly soon have been per- 

 ceived by every person who was acquainted with the method I used for sweeping 

 the heavens ; and as the same is practicable, not only with my telescopes, but 

 also with transit Instruments, and mural quadrants, we are now much indebted 

 to the Rev. Mr. Wollaston, who in the year 1789 favoured the astronomical 

 world with a work of nearly a similar construction with that which I was in the 

 habit of using ; but much enlarged, and enriched with stars taken from the best 

 authors; and reduced to the time of the year 17 90. We now seem only to 

 want an atlas on the same construction, on a scale equally extensive, and plenti- 

 fully stored with well ascertained objects. 



The micrometer-motion which is required for sweeping the heavens, and in- 

 deed for viewing the planets or other objects, is obtained by means of the end of 

 the rope which draws up the telescope. This goes down to a barrel ]2 inches 

 long, and 4 in diameter, joined on the same axle with another barrel, 12 inches 

 long, and 12 in diameter. A smaller rope goes from the largest barrel into the 

 working-room, where it is fastened to the top of a thin vertical spindle, 2 feet 

 6 inches long, and 3 inches in diameter. Another rope of equal size is fastened 

 to the bottom of the same spindle ; and when by turning the handle, the former 

 rope is wound on the spindle one way, this rope is wound oft' the contrary way. 

 This 2d rope goes out of the work-room over a pulley, which leads it upwards 

 to the top of the middle cross beam of the ladders, where it descends over ano- 

 ther pulley, by a weight with shifters which is suspended to the end of it. In 

 this manner a balance is obtained between the stress of the ropes, which leaves 

 the spindle at rest in any position where it may chance to stand, and considerably 

 eases the labour of the workman, who turns this handle a certain number of 

 times one way, and then the same number of times back again. By such a 

 motion of the handle the telescope is alternately depressed and elevated ; and 

 this being continued for as long a time as the observer chooses, enables him to 

 review the heavens as they pass by the telescope. 



