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LXX. Memoir on a new and certain Method of ascertaining the 

 Figure of the Earth hy means of Occultations of the fxed 

 Stars. By A. Cagnoli. With Notes and an Appendix ly 

 Francis Baily, 



[Concluded from p. 360.] 

 APPENDIX. 



feiNCE the original publication of the preceding Memoir, I am 

 not aware that any attempts have been made to derive any prac- 

 tical result from the theory of the learned author; notwithstand- 

 ing the simplicity of the method which he has proposed. Per- 

 haps no practicable mode, which has been hitherto suggested for 

 determining the true figure of the earth, or the precise quantity 

 of the compression of the polar axis, is entirely free from errors : 

 but, as those errors probably arise from different sources, accord- 

 ing to the methods adopted, it is desirable that the modes of in- 

 vestigating it should be varied as much as possible, in order that 

 the existing discordances may be ultimately reconciled or re- 

 moved. 



M. Lalande has &t?Aed.{BilliographieAslronomiqxie,^2ige.&\Z) 

 that in the Ephemeris of Vienna for 1791 there is " a dissertation 

 on the figure of the earth by M. Triesnecker ; who has deduced, 

 from sixteen occultations, the compression = -x^-^." Whether 

 the occultations, which were used by M. Triesnecker in his cal- 

 culations, were the peculiar sort of occultations alluded to by 

 M. Cagnoli, I am unable to ascertain ; as I have not been able 

 to procure a sight of M. Triesnecker's labours on this subject: 

 but, as that work was published two years before this Memoir, I 

 much doubt whether his method is precisely the same as that laid 

 down by M, Cagnoli. However this may be, the design of the 

 present translation is not at all affected thereby; as my object is to 

 recall the attention of the public to the subject, in order that the 

 benefit and advantage of the method may not be wholly lost; and 

 that such scientific persons, as may be induced to co-operate 

 therein, may look out for those peculiar occultations which are 

 described in the preceding pages, and note down their observa- 

 tions thereon accordingly. 



For this purpose, nothing more is requisite than a telescope 

 sufficiently powerful to see the star distinctly, when close to the 

 illuminated side of the moon's disc ; together with a good clock, 

 or watch, beating seconds. And although it would be desirable, 

 in all observations of this kind, to have the exact mean time of 

 the immersion and emersion of the star, yet, as it is the duration 

 only from which the consequences are to be deduced, it will be 

 sufficient (the latitude and longitude of the place being well as- 

 certained) 



