188 THEORY OF THE EA11TH. 



This result would assuredly be very striking, 

 had it heen directly, and by observations, made 

 upon Sirius itself, that they had fixed the length 

 of the year of Sirius. But experienced astrono- 

 mers affirm it to be impossible that the heliacal 

 rising of a star could afford a sufficient foundation 

 for exact observations on such a subject, especially 

 in a climate where the circumference of the ho- 

 rizon is constantly so much loaded with va- 

 pours, that, in clear nights, stars of the second 

 or third magnitude can never be seen within 

 some degrees of the verge of the horizon, and 

 that the sun itself is completely obscured at its 

 rising and setting. * They maintain, that, if 

 the length of the year had not been otherwise as- 

 certained, there would have been a mistake of one 

 or two days, f They have no doubt, therefore, 

 that this duration of 365 days and a quarter, is 

 that of the tropical year inaccurately determined 

 by the observation of the shadow, or by that of 



tied Recherches sur les Sciences et le Gouvernement de 

 1'Egypte. 



* These are the words of the late M. Nouet, Astronomer 

 to the Expedition to Egypt. See Volney, New Inquiries 

 regarding Ancient History, vol. iii. 



t Delambre, Abrege d' Astronomic, p. 217 : and in his 

 note upon the Parantaellons, in his History of ,the Astro- 

 nomy of the Middle Age, p. lij. 



