238 On a new Calculation of the 



destroyed these hopes. The confinement occasioned by his 

 accident prevented his availing hin^self of the season proper 

 for such operations, and which he would so usefully have em- 

 ployed. When able to resume his labours, the Spanish Go- 

 vernment refused him passports, and detained him prisoner, 

 with liberty to choose his place of abode. He chose Bar- 

 celona, to be as near as possible to Montjouy, which he was 

 forbidden to enter, and where the preceding year he had ob- 

 served the latitude of the centre of the tower of the fort. That 

 he might make his residence useful to astronomy, whilst pre- 

 vented from pursuing the special object of his mission, he 

 applied himself to determine the obliquity of the ecliptic ; and 

 thus, necessarily, the latitude of his new station. Reflecting 

 afterwards that this latitude might be rendered useful as a 

 verification of that of Montjouy, he connected the two stations 

 geodesically. In following carefully the record of his opera- 

 tions, we cannot fail to recognize his studious endeavour to 

 render the results obtained at the two stations dependent on 

 the same elements, and therefore strictly comparable. He 

 employed, for example, at both stations, the same instruments, 

 the same modes of adjustment and observation, (with very few 

 exceptions) the same stars, and the same elements to reduce and 

 calculate his results. Throughout we observe that exceeding 

 care, those minute precautions, and unvarying habits of pre- 

 cision, which are so universally allowed to this skilful observer. 

 The series in each star proceed regularly, and all the stars are 

 in accord, with the exception of one, although several are in 

 positions exceedingly unfavourable to exactness of observation. 

 His zeal, however, and his efforts, led to a most unexpected 

 conclusion. The comparison of the latitudes of Montjouy and 

 Barcelona, given in the second volume of the Measurement of 

 the Arc of the Meridian, presents a difference of 3' .25 greater 

 than is due to the well ascertained distance between the places 

 of observation. It has been attempted to explain this dif- 

 ference on two suppositions; first, a want of verticality in 

 the plane of the instrument ; and second, a deviation of the 

 plumb-line at Barcelona, caused by the attraction of Montjouy. 

 But the magnitude of the deflection of the plane from the ver- 

 tical, necessary on the first supposition, and a careful exami- 

 nation of the locality not being found to correspond to the 



