420 Zach on Repeating Circles. ■ 



might have been better employed with non-repeating instru- 

 ments. We do not dispute that this charge may be well 

 founded with regard to the great observatories which are fur- 

 nished with those large non-repeating instruments ; but we 

 think the general accusation as unjust as it is ill-founded. 

 We may reckon in Europe twelve mui'al quadrants con- 

 structed by the first artists of England, by Bird, Sisson, 

 Ramsden; without counting the two in the Royal Observatory 

 at Greenwich, that in the Observatory of Gottingen, and that 

 in the Observatory at the Ecole Militaire at Paris, which 

 Bradley, Maskelyne, Mayer, and La Landc, have used with 

 so much assiduity; — what has been doiie with the others ? 

 AVhere ai'e the observations and the catalogues of stars which 

 they have produced? Repeating circles were not invented 

 at the time they were constructed ; at any rate they were not 

 in use, and consequently could not prevent the use of other 

 instruments, nor retard the observations which might have 

 been made with them. 



We are acquainted with six of Reichenbach's three-foot 

 repeating circles distributed among five of the great obser- 

 vatories of Europe, without reckoning that at Milan which 

 M. Oriani has employed in his labours ; — what has been done 

 with the others? Nothing at all. It follows, then, that these 

 instruments have not occasioned loss of time, and have not 

 prevented, stopped or retarded the observations which might 

 have been made with the twelve mural quadrants, and with 

 the seven sectors ; all constructed by the greatest artists of 

 London. If we are asked the true and precise reason of this 

 dearth of observations which is so much complained of, we 

 shall give it in few words. It is, that in eveiy observatory 

 where there are good repeating or non-i-epeating instruments, 

 there is not at the same time a Bradley, a Maskelyne, a Pond, 

 a, Brinkley, a Mayer, a La Lande, a Piazzi, an Oriani, a Bes- 

 sel, a Struve, or a Littrow. 



it is not, in fact, so great as it has been represented. M. Oriani employs only 

 three or four minutes of time in making the observation of a star by four 

 rspetitions. For the zodiacal stars he makes only two repetitions, and ex- 

 pends only a minute, and often only 30 or 40 seconds. lie has generally 

 been contented with four repetitions (and that is sufficient) ; he has never 

 exceeded eight. (See the Appendices aux Ephcm. Ast. de Milan for the 

 years 1812 and 1813.) ''Ye should like to know whether Piazzi, in making 

 one observation, does not consume as much or even more time in turning 

 his circle and in reading the revolution* and the parts of his four micro- 

 scopic micrometers. 



LXXXW On 



