Zach ofi Repeating Circles. 4 1 5 



the same kind and of the same dimensions, and certainly of a 

 very inferior quality, in operations which involved the most 

 serious and important consequences. 



Thus we are neither the first nor the only persons who have 

 thought it possible to effect with a small circle what ought 

 only to have been undertaken with large instruments. Two 

 of the greatest astronomers and geometricians of Germany, 

 not only thought but did the same thing, and even more. 

 The celebrated Professor Gauss of Gottingen was of opinion 

 not only that whatever could be done with a large repeating 

 circle might be done as well with a small one, but was even 

 inclined to prefer the results obtained by means of the latter. 

 See the 1st vol. of my Correspondance Astronomiquei in which 

 will be found the following passage (p. 457) : 



" The Baron de Lindenau wrote to me some time ago, that 

 M. Gauss inclined rather towards the results obtained by 

 small circles, than towards those obtained by large ones. It 

 would be not only curious but very instructive to know the 

 reasons which have determined this great geometrician, who 

 is at the same time an astronomer not of the closet, but of 

 the starry heavens, in forming so important a judgement." 



Professor Gauss did not confine himself merely to thinking 

 and saying ; he also acted. In the xxviith vol. of our Cor- 

 respondance Astronomique Allemande (p. 481) will be found the 

 observations of the latitude made by this able astronomer at 

 the Observatory of Gottingen in the year 1813 with a Reichen- 

 bach's 12-inch repeating circle similar to ours. It will there 

 be seen that the greatest differences, as was the case in our ex- 

 periment, and in those made with all the large circles, did not 

 exceed 2",55. The mean of four latitudes obtained by two 

 stars observed above and below the pole, gave a difference of 

 only 1",80, and this latitude differed only by 1",6 from that 

 which Tobias Mayer had determined with his large and beau- 

 tiful Bird's 6-foot mural*. But what will this great English 

 artist say when he sees that M. Besself at Koningsberg, with 

 one of Cary's 18-inch pygmies, also ventured to attack the 

 8-foot meridian colossus at Greenwich, and affirms that he 

 detected it in an error of 5 and 6 and even 7 seconds? 



We shall not here enter into a discussion as to the point on 

 which side lies the fault of these great differences. It is suffi- 

 cient for the object we have in view, to show tliat such ano- 

 malies have been found, and announced as real, by one of our 

 first astronomical observers, whatever be the instrument with 

 which they were obtained. 



» Atlraciioii des Monta^ncs, p. 449. Corres. Ad. vol. ii. p. 64. 

 -j- Cor. Alt. vol. vii. cahier iii. p. 27 1. 



M. Bessel 



