57 



stein ) is composed of two distinct rocks ; one, 

 extremely compact and quartzose, with a small 

 portion of cement, and scarcely any fissures of 

 stratification, lies on a schistose gritstone ( sand- 

 steinschiefer) , with a fine grain, and divided 

 into an infinite number of small strata, ex- 

 tremely thin, and almost horizontal. It is pro- 

 bable, that the compact and quartzose stratum, 

 when the crevice was formed, resisted the shock 

 which rent these mountains ; and that it is the 

 continuity of this stratum, which serves as a 

 bridge to cross from one side of this valley to the 

 other. This natural arch is fourteen metres and a 

 half in length, and twelve metres seven decime- 

 tres in breadth : its thickness in the centre is two 

 metres four decimetres. Experiments carefully 

 made on the fall of bodies, and with a chro- 

 nometer by Berthoud, gave us ninety-seven 

 metres seven decimetres for the height of the 

 upper bridge above the level of the waters of the 

 torrent. A well informed person, who has an 

 agreeable country residence in the beautiful 

 valley of Fusagasaga, Don Jorge Lozano, had 

 already measured this height with a line, and 

 found it to be one hundred and twelve varas 

 (93*4 m ) ; the mean depth of the torrent appears 

 to be about rix metres. The Indians of Pandi 

 have formed, for the safety of travellers, who, 

 however, seldom visit this desert country, a 



