£(H) dr. Gregory's strictures on don Rodriguez, 



correct nesa cr incorrectness of the English observers might 

 have been proved in a way from which there could be no 

 appeal. Though, to be sure, if that plan had been adopted, 

 and the English results had, in consequence, been verified, Don 

 Rodriguez's paper could never have appeared. 



There is, however, a method of determining the point, 

 oven without taking this trouble. Having then shown, I trust 

 satisfactorily, that Don Rodriguez's reasons for imputing an 

 error of 4 or 5 seconds to the English observations, are nuga- 

 tory^: I shall now proceed, with all possible conciseness, to show 

 that there cannot he an error of one second either in the obser- 

 vations at Arbury Hill, or at Dunnose; and those at Clifton are, 

 by the Don's own concessions, out of the question. 

 The mode of First, the manner of fixing the zenith sector could not lead 

 *^ith^ tb tor Ze " t0 error > for > " to P roc ure for the external stand (says Col. 

 precludes er- Mudge, Phil. Trans. 1803) and thence for the whole apparatus, 

 ,or ' a firm foundation, I caused four long stakes to be driven into 



the ground, one for each foot of the stand, to which its feet 

 were firmly screwed down. The surfaces of the stakes were 

 cut off smooth, and brought into the same horizontal plane, 

 by which means the interior frame and sector were placed much 

 within the limits of their several adjustments." The whole 

 was enclosed in a suitable observatory. 



Don Rodriguez may perhaps think the French method of 



fixing their instruments, on some occasions, preferable to this. 



French obner-The reader shall judge. Their instruments, both for taking 



vations atCha- ho r i zonta i an( j vertical angles, were sometimes placed on tot- 



during a high tering stages, so as to give anomalies in the angles from 5 '* to 



wind, on a q// furnishing, as Delambre terms them, " le tourment des 



stage so tot'er- 3 %*,, „ tm i-. i- • 



ing, that even observateurs. Thus, at p. 40, Discours Preliminaire, we are 



a little breeze xo\d that at Chatillon, there was a high wooden stage erected 

 much disturb- „ , . . . , , , , „ , 



ed the observ- * or an observatory, m which the carpenter had so badly done 



crK * his work, that " le meindre vent agitoit toute la machine, de 



maniere n©n settlement a rendre les observations moins sures, 



mais ainquieter les- observateurs." And on turning to p. 174, 



tome i. it will be seen that the observers had not to contend 



with a gentle gale j for they there tell us of the " Grand vent 



qui ngiioit le signal et 1'instiument." The whole was blown 



down shoi tly after. Will Don Rodriguez place reliance on 



observations made from such a platform in such a wind ; and, 



notwithstanding, 



