280 THE SEA. 



but as it was a strong attraction to visitors, he caused the instrument to be dismantled. About 

 the year 1847 Mr. Lerebours offered to Greenwich observatory the largest refracting telescope 

 which had ever been constructed. The temptation was certainly a great one ; it would have 

 been flattering to the self-esteem of the institution to have possessed a wonder of this sort, 

 unique as it was in the world. Mr. Airy need only to have said the word, and the Lords of the 

 Admiralty would assuredly have made the purchase. But the Astronomer, on the contrary, 

 held the present aloof with a determined hand. What was it that he feared ? The perfidious 

 influence of such a siren, which, by concentrating attention on the beauties of the heavens, 

 would perhaps have turned away the attention of the assistants from their daily task, and have 

 compromised the success of the Observatory. 



" An observation of the sun takes place at least once a week at mid-day, in the transit 

 circle room, and a large portion of the staff of the establishment take a part in it ; but it is 

 at night that one can form the best idea of the mode in which the transit of the heavenly 

 bodies over the meridian is duly verified. 



"The first observations made with the new transit circle date from 1851, and, from 

 that time to the present they have never been discontinued. The assistant who is appointed, 

 aided by this instrument to watch the state of the heavens, is on guard for twenty-four 

 hours, i. e., from three in the morning until three a.m. the next day. Except under extra- 

 ordinary circumstances, the same duties are never assigned to an assistant two days running. 

 Having already worked some hours after sunset, he goes home to take his evening meal, and 

 when he returns into the transit circle room it is quite night. The shutters, which, during 

 the day shut in a part of the ceiling, are now unclosed, and by means of this aperture the whole 

 sky seems thrown open to the room. 



" Having consulted his list, and adjusted his telescope, he commences his steady gaze. 

 His intentness can only be compared to that of a sportsman, or still better to that of a pointer 

 dog, only, instead of a partridge or a woodcock, he is eagerly waiting to see a star get up. 

 There it is at last ! It comes into view quick and sudden as a meteor. Scarcely has it entered 

 into the telegraphic field of sight than it appears to approach rapidly some objects which look 

 like a series of transverse iron bars placed at equal distances from each other. These, however, 

 in reality, are nothing but threads of the thickness of a spider's web, stretched according to a 

 system in the interior of the telescope, and wonderfully magnified by the power of the lenses. 



" The assistants are all astronomers by profession, and their eyes have been well trained by 

 continual practice. How, then, can it happen, that their observations do not always prove 

 accordant one with another ? There is a physiological mystery hidden in the fact which it 

 would be interesting to penetrate. Each observer, although operating with the same instrument 

 and guided by the same plan, perceives a celestial phenomenon as, for instance, the transit of a 

 star either sooner or later than another does. This variation is attributed to the idiosyncrasy 

 of the sense of sight in each individual, or to the more or less prompt manner in which the 

 eye telegraphs its impression to the brain. It must, of course, be quite understood that no 

 considerable inequalities of time are in question here ; it is, at the most, some fraction of a 

 second that I am alluding to ; but the astronomical transit observations are of so delicate a 

 nature, that the slightest errors would destroy their worth. Under these circumstances it has 

 been found necessary to establish an average or standard,, and each observer gets to know 



