Zach on Repeating Circles, 409 



take. The artist in question was therefore deceived, and la- 

 boured under a complete mistake, when he said that we 

 had broxight out a density of the earth nearly coinciding 

 issith the Schehallien experiment and with the more recent 

 one which Cavendish obtained by direct attraction. Not a 

 w^ord of all this was to be found in our work. This celebrated 

 artist informs us again in his very instructive and interesting- 

 paper, that " it is possible that a result might have been 



obtained of an equal quantity contrary to attraction." But if 

 he had properly read or understood our work, he would have 

 found that not only we had said the same thing, but that we 

 actually expected this contrary result. 



We extract what we said on this subject (p. 358): " We will 

 candidly confess that in undertaking this work we were not 

 without apprehension, that instead of finding the effect of an 

 attraction we should find that of a repulsion ; that is to say, 

 an absurdity which would have only served to prove the insuf- 

 ficiency of our mechanical and physical means for determining 

 a quantity so minute. We were not ignorant that this had 

 happened to M. Mechain at Barcelona and Montjouy in his 

 search for a quantity almost double that which we were going 

 to seek." And further (p. 359) : " We have formally de- 

 clared that, so far from seeking the cause of these anomalies 

 in local attractions, or in the irregulai'ities of the density of 

 strata of the earth, we were much more inclined to lay the 

 blame on the instruments, and even on the observations. We 

 have since seen that Don Rodriguez, in his ingenious exami- 

 nation of the three degrees of the meridian measured in En- 

 gland, held this opinion in common with us." If we had be- 

 lieved in the reality of our result, and if that belief had been 

 erroneous, we at least had, as companions in error, Bouguer, 

 De la Condamine, Maskelyne, Mechain, and Delambre, who 

 all held the same belief, and even for quantities much smaller 

 than ours ; for M. Delambre, in fact, speaks of 0",65 of the 

 attraction of mountains found with 13 and 15 inch repeating 

 circles of Lenoir. In the second volume of the Base Metrique^ 

 he says (p. 631) : "At Dunkirk it appears that the inequality 

 of attraction must be very small, since the distance from the 

 tower to the sea is more than 1000 toises." And hei-e we 

 must remark diat his observations of latitude differ from those 

 of Mechain by 0",65 ; upon which he asks, " Can this small 

 diflference be caused by the unequal densities of the eardi?" 



At least we did not mistake the direction of this result; we 

 did not take rcj)ul..ion for attraction, as belell a great astrono- 

 mer and geometrician; a circumstance which we have re- 



Vol. 61. No. 302. June 1823. 3 F corded 



