undertaken ui the Konigsbcrg Observatory. 431 



without interruption ; and are concluded bv a repetition of the 

 readings ot" the microscope and the meteorological instrument. 

 In case no other observations should prevent, a new zone will 

 be examined after half an hour or an hour; so that three hours 

 of right ascension will be observed regularly every niglit. 



The zones are so arranged that the middle of them falls on 

 some even degree of declination. And in order that no chasm 

 may exist between two contiguous zones, as well as to prevent 

 a repetition of the same observations, I have taken the breadth 

 of the zone somewhat more than two degrees: viz. 2'^ 12'. 

 At first the magnifying power of 66 was employed ; but I soon 

 Ibund out that it was too small for so powerful a telescope, and 

 I therefore took, from the 1 1th zone onwards, one of 107 maf- 

 nifying power, which has, in fact, less light, and gives some- 

 what more satisfactory observations. 



In an undertaking of this kind, which requires the applica- 

 tion of many years, the greatest oeconomy of time is necessary: 

 frequently must some other observation be sacrificed to It, 

 which nevertheless, from the opposition of the planets, neither 

 has yet, nor may be, the case. The number of the zones from 

 the 19th of August to die end of 1821, has however only 

 amounted to 39, and up to d)is time (17th June 1822) to 89; 

 from which it may be inferred how universally bad the weather 

 has been during that period. These observations (with only 

 two exceptions) fall collectively between —5° and 4-15° of 

 declination ; and seldom extend beyond stars of the 9th mag- 

 nitude. It will however be necessary to describe somewhat 

 more in tletail what kind of stars I mean ♦;o class under the 

 9th magnitude, in order to prevent any differences between 

 different astronomers. Tobias Mayer, Piazzi, and the Histoire 

 Celeste appear to agree exactly: but Bradley for the most part 

 denotes the stars by a greater magnitude. Maskelyne, on the 

 other hand, has observed stars to which he attributes the 10th 

 11th, and 12th magnitudes; which last, by a scale agreeing 

 with the Histoire Celeste, he could hardly' have seen in the 

 telescope of his mural (juadrant. I have endeavoured to follow 

 the Histoire Celeste, and frequently agree with it. 



I ascribe the 9th magnitude to all those stars winch, with 

 a sufficiently powerful ilhnnination of the wires, I can see well 

 enough to lender them difhcult to pass unobserved through 

 the field of view, on moving the telescope. Stars of the 9th 

 and 10th magnitudes are more difficult to discover, and for 

 the 10th magnitude, even in my telescope of an aperture of 

 lour inches, the light must be so much diminished, tliat the 

 wires can no longer be seen with any distinctness. What stars 

 1 arrange untler the dilfereut magnitudes will be more clciirly 



seen 



