180 Mr. Pond on the Changes in the 



southward stars have a greater tendency to deviation than the 

 northern ones. 



It' we select fi'om the preceding tables tiiose stars which 

 were least frequently observed, at one or nW ot'tlie three pe- 

 riods, we shall find that they all tend to conllrin the Ibregoing 

 general results ; though they must be regarded as doing so 

 rather by their united effect, than by their weight of evidence 

 when considered singly. Stars that have lieen but seldom ob- 

 served, give results considerably afl'octed by accidental eiTor 

 of observation ; which error is quite of a different nature from 

 that produced by permanent defect in the instrument, and 

 which repetition of observation has no tendency to remove. 



If the deviations of those stars that have been imperfectly 

 observed, were attributable either to error of observation, or 

 defect in the instruments, the deviation would either follow no 

 law at all, or some law depending upon zenith distance : but 

 the facts we have seen to be at variance with either of these 

 hypotheses. Not however to rest satisfied with these consi- 

 derations, drawn from the general tendency of all the stars 

 without exception, let us select some striking examples of de- 

 viation, in particular groups of stars, on which we might be 

 satisfied to rest the issue of this question. Of these groups I 

 have marked Jive in the table of stars arranged according to 

 north-polar distance, each of which we will take the pains to 

 consider more attentively. 



1. There are six stars in my catalogue north of y Draconis, 

 of which three are found to the north, and three to the south 

 of their computed places. These inequalities may appear at 

 first sight to be wholly accidental ; but if we pay attention to 

 the right ascension, we shall find that the three which appear 

 to the northward, are situated in that part of the heavens as 

 to right ascension where the southern deviation is the least 

 perceptible, and that the three which a})pear to the southward, 

 are in that part as to right ascension where the southern de- 

 viation is the greatest. But of these six stars there are two, 

 « Cassiopeice, and y Ursa; Majoris, which deserve fuither con- 

 sideration. These two stars are within less than one degree 

 of each otlier in polar distance, and consequently pass over 

 the meridian at nearly the same altitude. The observations 

 of Bradley on the stars north of the zenith are not so nume- 

 rous as could be wished ; but each of the two stars in question 

 was observed by him about five times towards the year 1 753 ; 

 that is, 60 years from the dale of my catalogue of 1 8 1 3. I have 

 carefully recomputed the predicted places of these stars, and 

 I find a Cassiopeice not less than \"'5 to the south of its pre- 

 dicted 



