168 COSMOS. 



phyrc instead of cavities, render it difEc:ilt, notwithstanding 

 the admirable simphcity of the method, to arrive at any great 

 result regarding the figure of the Earth from observation of 

 the oscillations of the pendulum. In the astronomical part of 

 the determination of degrees of latitude, mountain chains, or 

 the denser strata of the Earth, likewise exercise, although in a 

 less degree, an unfavorable influence on the measurement. 



As the form of the Earth exerts a powerful influence on the 

 motions of other cosmical bodies, and especially on that of" its 

 own neighboring satellite, a raiore perfect knowledge of the mo- 

 tion of the latter will enable us reciprocally to draw an infer- 

 ence regarding the figure of the Earth. Thus, as Laplace ably 

 remarks,* "An astronomer, without leaving his observatory, 

 may, by a comparison of lunar theory with true observations, 

 not only be ei^abled to determine the form and size of the 

 Earth, but also its distance from the Sun and Moon — results 

 that otherwise could only be arrived at by long and arduous 

 expeditions to the most remote parts of both hemispheres." 



declivity of Ararat, which with Caucasus may be said to lie in'the cen- 

 ter of gravity of the old continent formed by Europe, Asia, and Africa, 

 the very exact pendulum experiments of Fedorow give indications, not 

 of subterranean cavities, but of dense volcanic masses. (Parrot, Reise 

 zum Ararat, bd. ii., s. 143.) In the geodesic operations of Carlini and 

 Plana, in Lombardy, difierences ranging from 20" to 47"-8 have been 

 found between direct observations of latitude and the results of these 

 operations. (See the instances of Andrate and Mondovi, and those of 

 Milan and Padua, in the Operations Geodes. et Astron. pour la Mesure 

 d'v.n Arc du Parallele Moyen, t. ii., p. 347 ; Effemeridi Astron. di Mi- 

 lano, 1842, p. 57.) The latitude of Milan, deduced from that of Berne, 

 according to the French triangulation, is 45° 27' 52", while, according 

 to direct astronomical observations, it is 45° 27' 35". As the perturba- 

 tions extend in the plain of Lombardy to Parma, which is far south of 

 tlie Po (Plana, Op6rat. Geod., t. ii., p. 847), it is probable that there are 

 deflecting causes concealed beneath the soil of the plain itself. Struve 

 has made similar experiments [ with corresponding results] in the most 

 level parts of eastern Europe. (Schumacher, Astron. Nachrichten, 1830, 

 No. 164, s. 399.) Regarding the influence of dense masses supposed to 

 lie at a small depth, equal to the mean height of the Alps, see the ana- 

 lytical expressions given by Hossard and Rozet, in the Comftes Rendus, 

 t. xviii., 1844, p. 292, and compare them with Poisson, Traiti de M6 

 sanique (2me ed.), t. i., p. 482. The earliest observations on the in 

 riueuce which different kinds of rocks exercise on the vibration of the 

 pendulum are those of Thomas Young, in the Philos. Transactions for 

 1819, p. 70-96. In drawing conclusions regarding the Earth's curva- 

 ture from the length of the pendulum, we ought not to overlook the 

 possibility that its crust may have undergone a process of hardening 

 previously to metallic and dense basaltic masses having penetrated froa 

 gr*at depths, through open clefts, and approached near the surface. 

 ■ Laplace, Expos, du Syst. du Monde, p. 231. 



