g4) On the Royal Observatory at Palermo. 



tend his investigations as to other probable causes of this phae- 

 nomenon. 



Amongst the various causes that might be assigned for this 

 remarkable anomaly M. Cacciatore imagined that the heat of 

 the sun on the circle might have the greatest effect : and he 

 has entered into an elaborate investigation of the subject with 

 a view to determine this curious point. We have not room 

 for a detail of the steps of the process pursued by this learned 

 astronomer : but it may suffice at present to state that, on the 

 presumption that the circle was divided at the temperature of 

 54° Fahr. (which, he informs us, was the case) the corrections 

 for the readings of the microscopes on the limb will be 

 For the summer solstice = {t — 54°) x 0",06931 

 For the winter solstice = {t - 54°) x 0",29133 

 By the help of these formulae, and the application of the me- 

 thod of minimum squares, he finds the mean obliquity for 

 January 1, 1809, to be as under: viz. 



From the summer solstice = 23° 27' 5l",57 340 obs. 



From the winter solstice = 23 27 51 ,75 182 obs. 

 whence he deduces the mean obliquity, regard being had to 

 the number of observations, to be on January 1, 1809, equal 

 to 23° 27' 51",64. He then compares this result with the de- 

 terminations by other astronomers, reduced to the same epoch, 



which are as follows ; viz. 



Mean Obliq. Jan. 1,1809. 



Cacciatore 23° 27' 51",64 



Piazzi 52,04 



Oriani 51 ,34 



Arago 51 ,50 



Pond 51 ,32 



Bessel 50,10 



Arithmetical mean = 23° 27' 51 ",33 

 M. Cacciatore next investigates the subject of the annual 

 diminution of the obliquity of the ecliptic, and deduces the fol- 

 lowing results from a comparison of the observations of the 

 mider-mentioned astronomers : viz. 



Piazzi = 0",4546 



Maskelyne .... = 0,4355 



Mayer*. = 0,4620 



Bradley = 0,4437 



La Cailie =0 ,4650 



The mean of these is 0",4522, but M. Cacciatore is disposed 

 to reject the result deduced from La Caiile's observations; 

 which will therefore reduce the value rather below 0",45. 



He 



