100 BAILLY. 



problematical correctness. Finally, to complete the ob- 

 servation, he must read off the microscopical divisions 

 of the graduated circle, and for what opticians call in- 

 dolent vision (the only sort that the ancients ever re- 

 quired) must substitute strained vision, which in a few 

 years brings on blindness.* 



When he has scarcely escaped from this physical and 

 moral torture, and the astronomer wishes to know what 

 degree of utility is deducible from his labours, he is ob- 

 liged to plunge into numerical calculations of a repelling 

 length and intricacy. Some observations that have been 

 made in less than a minute, require a whole day's work 

 in order to be compared with the tables. 



Such was the view that Lacaille, without any soften- 

 ing, exhibited to his young friend ; such was the profes- 

 sion into which the adolescent poet plunged with great 

 ardour, and without having been at all prepared for the 

 transition. 



A useful calculation constituted the first claim of our 

 tyro to the attention of the learned world. 



The year 1759 had been marked by one of those great 

 events, the memory of which is religiously preserved in 

 scientific history. A comet, that of 1682, had returned 

 at the epoch foretold by Clairaut, and very nearly in the 

 region that mathematical analysis had indicated to him. 

 This reappearance raised comets out of the category of 

 sublunary meteors ; it gave them definitely closed curves 



* This long list of supposed difficulties in making an exact observa- 

 tion is hardly worthy of a zealous astronomer. Our author shows no 

 enthusiasm for his subject here, and ends by ascribing the whole 

 Jeremiad to Lacaille, a man of veiy great practical perseverance. It 

 is to be regretted that Arago never refers to observations of his own, 

 but constantly quotes from others, nor does he always select the best. 

 Translator's Note. 



