274 



to six thousand feet, have been hitherto only 

 from 4 to 6 feet deep. The difficulties naturally 

 increase with the elevation of the ridge of par- 

 tition, the depth of the excavations, and the 

 size, if not the multiplicity, of the locks. It is 

 not enough to dig the canal ; it must be ascer- 

 tained that the quantity of water derived from 

 the upper ground is equal to the demand for 

 filling it ; that is, sufficient to feed the canal, 

 and to replace what is lost by the locks, by eva- 

 poration, and by nitration. We have seen above 

 that the local circumstances in the isthmuses of 

 Cupica and Huasacualco are such, that the ob- 

 stacle to be overcome in effecting the junction 

 of the seas, is less the height of the ridge which 

 the canal must cross, than the state of the beds 

 of the rivers (Naipi and Rio del Passo) which 

 must be rendered navigable, either by being ex- 

 cavated by machines worked by a steam-engine, 

 or by wears and lateral derivations. In the in- 

 tendance of Nicaragua, the great depth of the 

 Rio San Juan, and that of the lake of Nicaragua, 

 or laguna de Granada, which is, according to 

 Mr. Robinson, from 17 to 40 ; and, according 

 to Mr. Juarros, from 20 to 55 feet, seems to 

 render such labors superfluous *. The moun- 

 tains of the isthmus of Panama rise probably 

 to the elevation of the basins of partition 



* Compendio de la Hist, de Gitat'mala, T. i, p. 51. This 

 work ie 12 years anterior to that of Mr. Robinson. 



