50 



which is not transition limestone, though it con- 

 tains beds of schistous jasper (hieselschiefer) . 



It is impossible to cross the steppes or savan- 

 nahs of South America, without indulging the 

 hope, that science will one day profit from the 

 many advantages they offer, above any other 

 region of the Globe, for measuring the degrees 

 of a terrestrial arch in the direction of a 

 meridian, or perpendicularly to the meridian. 

 Their great extent from east to west would 

 render the measurement of some degrees of 

 longitude extremely easy ; and this operation 

 would be very interesting with respect to the 

 precise knowledge of the figure of the Earth. 

 The llanos of Venezuela are thirteen degrees 

 east of the places, where, on the one side, the 

 French academicians, by triangles resting on 

 the summits of the Cordilleras, and on the other, 

 Mason and Dixon, renouncing (in the plains 

 of Pennsylvania) the aid of trigonometry, execu- 

 ted their measurements ; and they are nearly on 

 the same parallel, which is a very important 

 circumstance, as the table-land of India, between 

 the Jumna and Madura, which was the theatre of 

 Colonel Lambton's excellent operations. What- 

 ever doubts may yet be entertained concerning 

 the precision of instruments, the errors of obser- 

 vations, and the influence of local attractions, it 

 would be difficult in the present state of our 

 knowledge, to deny the inequalities of the flat- 



