On the Royal Observatory at Palermo. 83 



a bending of the metallic wires in the focus of the telescope : 

 2° a bending of the telescope itself; each vai'ying according 

 to the temperature of the atmosphere : 3° a want of informa- 

 tion as to the true value of the mean refraction, or the correc- 

 tions to be applied thereto : 4° a modification of the rays of 

 light by the action of heat. The first two he gives up as 

 groundless : and to the last he does not attach much import- 

 ance. With respect to the refraction, he has shown that it 

 cannot, under any circumstances, account for the whole of the 

 difference ; although it is possible that a portion of that dis- 

 cordancy may be occasioned thereby. In order to set this in a 

 clearer point of view, he has given a small table (which we shall 

 here subjoin), in which is contained the amount of refraction 

 according to the several tables of Piazzi, Carlini, Delambre, 

 Young, and Bessel, on the day of the summer and winter sol- 

 stices respectively, for the several observatories of Palermo, 

 Milan, Paris, Gi'eenwich and Konigsberg. The altitude of 

 the sun at each place, on those days, is added ; together with 

 the assumed mean state of the thermometer. The barometer 

 has been assumed equal to 29*6 inches. These elements are 

 sufficiently correct for the comparisons proposed. 



Summer Solstice. 



Winter Solstice. 



It is evident, iherefon-, that the difference between the two 

 solstices cannot wholly arise from the tables of refraction cm- 

 plovcd : and M. Cacciatore was consequently induced to ex- 



M 2 tend 



