OP THE EARTH. \ 59 



Galileo who lirst observed when a boy, (having, probably, 

 differed his thoughts to wander from the service,) that the 

 neight of the vaulted roof of a church might be measured by 

 the time of the vibration of the chandeliers suspended at dif- 

 ferent altitudes, could hardly have anticipated that the pen- 

 dulum would one day be carried from pole to pole, in order to 

 determine the form of the Earth ; or rather that the unequal 

 density of the strata of the Earth, affects the length of the 

 seconds pendulum by means of intricate forces of local attrac- 

 tion, which are, however, almost regular in large tracts of 

 land. These geognostic relations of an instrument intended 

 for the measurement of time this property of the pendulum, 

 by which, like a sounding line, it searches unknown depths, 

 and reveals in volcanic islands,* or in the declivity of elevated 

 continental mountain chains,f dense masses of basalt and 



America in July, 1744. The most necessary and useful amendment to 

 the numbers on this inscription would have been the astronomical longi- 

 tude of Quito. (Humboldt, Recueil dWbs&rv. Astron., t. ii. pp. 319-354.) 

 Nouet's latitudes, engraved on Egyptian monuments, offer a more recent 

 example of the danger presented by the grave perpetuation of faice or 

 careless results. 



* Respecting the augmented intensity of the attraction of gravitation 

 in volcanic islands, (St. Helena, Ualan, Fernando de Noronha, Isle of 

 France, Guam, Mowi, and Galapagos,) Rawak (Lutke, p. 240) being an 

 exception, probably in consequence of its proximity to the high land of 

 New Guinea, see Mathieu, in Delambre, Hist, de T Astronomic, au 

 ISme Siecle, p. 701. 



t Numerous observations also show great irregularities in the length 

 of the pendulum in the midst of continents, and which are ascribed 

 to local attractions. (Delambre, Mesure de la Meridienne, t. iii. p. 

 548; Biot, in the Mem. de I'Academie des Sciences, t. viii., 1829, 

 pp. 18 and 23.) In passing over the South of France and Lombardy, 

 from west to east, we find the minimum intensity of gravitation 

 at Bordeaux ; from thence it increases rapidly as we advance eastward, 

 through Figeac, Clermont-Ferrand, Milan, and Padua; and in the last 

 town we find that the intensity has attained its maximum. The influ- 

 ence of the southern declivities of the Alps is not merely dependent on 

 the general size of their mass, but (much more) in the opinion of Elie 

 de Beaumont, (Rech. sur les Revol. de la Surface du Globe, 1830, p. 729,) 

 on the rocks of melaphyre and serpentine, which have elevated the chain. 

 On the declivity of Ararat, which with Caucasus may be said to lie in 

 the centre 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 

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



