NOTES. xv 



may be estimated." (Tend. Exp. p. 341 .) Tlie work from which this passage 

 is taken was published before M. Mathieu's notice in Delambre's History of 

 Astronomy, and is referred to by M. Mathieu in the passage to which M. de 

 Humboldt alludes. EDITOB.] 



( 133 ) p. 158. Numerous observations shew great irregularities in the 

 length of the pendulum in continental as well as in insular and littoral locali- 

 ties, and which are also ascribed to local attraction. (Delambre, Mesure de 

 la Meridienne, T. iii. p. 548; Biot, Mem. de 1' Academic des Sciences, 

 1829, T. viii. pp. 18 and 23. In crossing the south of France and Lombard/ 

 from west to east, we find a minimum of intensity of gravitation at Bordeaux 

 thence it increases rapidly at the more eastern stations of Figeac, Clermont- 

 Ferrand, Milan, and Padua, at which last city it reaches a maximum. In 

 the opinion of Elie de Beaumont (Recherches sur Ics Revolutions de la 

 Surface du Globe, 1830, p. 729), the influence of the Alps on the variations 

 of gravitation on their southern side is not alone to be ascribed to their 

 mass, but still more to the rocks of melaphyre and serpentine which have 

 elevated the chain. On the slope of Mount Ararat (which, with Caucasus, 

 may be said to be situated near the centre of gravity of the old con- 

 tinent, consisting of Europe, Asia, and Africa), Fedorow's very exact pen- 

 dulum experiments indicate likewise the presence of dense volcanic masses in 

 lieu of cavities (Parrot, Reise zum Ararat, Bd. ii. S. 143). In the geoJcsical 

 operations of Carlini and Plana in Lombardy, differences of 20" to 47".8 

 have been found between geodesical measurements and the direct determi- 

 nations of latitude ; see the instances of Andrate and Mondovi, Milan and 

 Padua, in Operations geodes. et astron. pour la mesure d'un arc du parallele 

 moyeu, T. ii. p. 347; Effemeridi astron. di Milano, 1842, p. 57. It 

 follows from the French triangulation that the latitude of Milan, deduced 

 from that of Berne, is 45 27' 52"; whereas direct astronomical observation 

 gives it 45 27' 35". As the perturbations extend in the plain of Lombardy 

 to Parma, far south of the Po (Plana, Operat. geod. T. ii. p. 847), we may 

 conjecture that there are deflecting causes in the plain itself. Struve has 

 met with the same anomalies in the most level parts of eastern Europe 

 (Schumacher, Astr. Nachr. 1830, Nr. 164, S. 399). On the influence of 

 dense masses supposed to exist at a small depth equal to the mean height of 

 the chain of the Alps, see the analytical expressions which Hossard and Rozet 

 have inserted in the Comptes-rendus, T. xviii. 1844, p. 292, and compare 

 them with Poisson, Traite de Mecanique (2 mt e"d.), T. i. p. 482. The 

 earliest notices of the influence which rocks of different kinds might exercise 



