1 84 Dr. Gregory's Strictures on Don Rodriguez. 



that an insular situation is very ill fitted to promote the 

 determination of the figure of the earth. 



Let us fee, however, how " satisfactorif former mea- 

 sures have been " by their agreevient," and how completely 

 they prove that the earth's surface is " very regularly " el- 

 liptical. Lacaiile's degree in lat. 43° N. coiiipared with 

 Boiiguer's at the equator, gives for the compression -^^J-g-. 

 The degree in Marvland, with Bouguer's equatorial, gives 

 ■54ir* ^ he Spanish degree at the equator, with the French 

 degree lat. 45°, gives -sl-^. Boscovich's Italian degree, lat. 

 43°, compared with Bouiiuer's at the equator, gives ^^. 

 Bishop Horsley, by a geometrical mean of twelve different 

 dlipticities, obtains -j-oVt- Boscovieh, taking a mean from 

 all the measures of dei^rees, so as to make the positive and 

 negative errors equal, obtains ^^-j.. Lalande, by compariiig 

 Father Leisganig's degrees in Germany with eight others 

 in different latitudes, gets ■—-. And the recent measures 

 in France give, as we have seen, -j-t"?- Such is a summary 

 of the evidence from which it is to be concluded that the 

 earth is <* elliptical," even " verv regularly so." General 

 Roy, who had got a habit, not very uncommon among 

 sciintific Englishmen, of deducing rca^-onablc conclusions 

 from anomalous appearances, and not twislins' them to 

 suit a fanciful hypothesis, assumed sevtn different spheroids 

 of varying ratios between -j-fg- and -\-o', and, on finding 

 that none of them corresponded so uniformly as might be 

 ■wished, with the operations in different laiitudes, made 

 these inferences : " Hence it is obvious, that the arcs of 

 an ellipsoid, however great or small the degree of its oblate- 

 ness may be, will not any way correspond with the mea- 

 sured portions of the surface of ihe earth." " Hence it is 

 that philosophers are not yet agreed in opinion with regard 

 to the figure of the earth ; some contending, that it has 

 no reguLar figure, that is, not such as would be generated 

 by the revolution of a curve around its axis." And aoain, 

 after specifying some other facts, " From all which we 

 may conclude, that the earth is not an ellipsoid." 



Nor is this opinion peculiar to Gen. Roy : it is common, 

 I believe, to all who have contemplated the subject, except 

 Don Rodriguei-. Thus, Puissant, at p. 187 ot his Gcndesie, 

 savs, " La comparaison des divers degres mesures a I'equa- 

 teur, en France, en Pensylvanie, etc. donne lieu a. decider 

 que les meridiens sont differens entr'eux, et n'ont pas la 

 iorme elliptique." And at p. 222, " D'ovj Ton doit con- 

 chire que la terre n'a poi?it la forme reguliere que Ton 

 gerait tente de lui attribuer." To the same purpose writes 



Laplace, 



