Zach on Repeating Circles. 417 



does not act like a meridian telescope, as the 3-foot meridian 

 circles of Reichenbach do, with the utmost perfection ; shall 

 we therefore assert, that we must sing a requiem over the con- 

 struction of this circle at Greenwich, and leave it to sta?id on 

 its o'uoii GREAT busc ? We are very far from thinking so ; 

 we know better how to do justice to the great artist who con- 

 structed this chsf-cVcsuvre, although he deceived himself in 

 thinking that it would act as a transit instrument. That this 

 is not one is amply proved by the numerous observations of the 

 astronomer royal. This detracts nothing either from the 

 merit of the instrument, which for taking polar distances is 

 perfect ; nor from the merit of the author of so extraordinaiy 

 a work, who is and who will always be one of the greatest 

 artists of his age. We have often heard the late Mr. Ramsden 

 say, that he would construct a sector with which he could de- 

 termine the length of his workshop ; that he would make ba- 

 rometers with which he w-ould measure the height of his desk, 

 &c. : all these were only fa(;ons de parlei; to express, that he 

 would do his utmost to give to his instruments every possible 

 degree of perfection ; and the hopes indulged by the artist 

 who constructed the mural circle at Greenwich, that this in- 

 strument might also serve as a transit, only prove that this great 

 man piu'siied his work with so much care and exactness, that he 

 thought his instrument would add, to all its other perfections, 

 that of serving as a transit instrument. Experience has, in- 

 deed, since proved the contrary. 



It is now the fashion to decry repeating circles. These in- 

 struments have certainly their defects, like all others, and we 

 were the first to discover and to point them out. Nevertheless 

 we ought to be just, and to give to every thing its deserts. We 

 have already asked above, with what other portable instru- 

 ment coidd we have accomplished what we did in our travels, 

 with a 12-incli rejjeating circle and an 8-inch repeating theo- 

 dolite? Mr. G. DoUond is much more just hi this matter, 

 and considers this sort of instrument with more candour antl a 

 more accurate perception of its real utility. This great opti- 

 cian, hi his description of a new 15-incli repeating circle of 

 his invention, inserted in the first volume of the Memoirs of 

 the Astronomical Society of London, says (p. 57): 



" The rej)eatirig principle upon which tlic instrument is 

 founded, is too well imderstoocl to require any explanation ; 

 I shall therefore only remark, tliat I consider it to be i)f very 

 great advantage to 'portnbh' instruments; particularly as they 

 cannot be prepared (on account of their })rice and dimensions) 



Vol. 61. No. 302. June 1823, 3 G with 



