NICARAGUA AND THE ISTHMIAN ROUTES 



251 



CASTILLO RAPIDS — TOWN AND FORT 



n it seriously obstruct navigation except in times of extremely 

 low water. Below this point the San Juan receives the waters 

 of a few streams, the principal of which are the Rio Poco Sol 

 and Rio Santa Cruz. Ten miles below Torro rapids are the 

 largest rapids on the river, at Castillo Viejo. As the river here 

 falls about five feet in a -few hundred feet, steamers are seldom 

 taken over except in high water. A railroad about 2,000 feet 

 long is provided for the portage of freight and passengers on the 

 right bank of the river. 



Below Castillo are the Diamond, Balas, and Machuca rapids, 

 the last-named being 13 miles from Castillo. All these rapids 

 admit the passage of river steamers, except at extreme low water. 

 Below Machuca there are no more rapids. The river is now 

 deep and sluggish for a distance of about 17 miles, until it re- 

 ceives the waters and sediment of the Rio San Carlos. This river 

 is the largest tributary of the San Juan, rising far to the south- 

 ward, in the mountains of Costa Rica, and bearing such a volume 

 of sediment that a delta has been built up at its mouth. From 

 this point to the sea the San Juan is a shallow stream with sandy 

 sli i fling bed ; 25 miles farther down the Serapiqui empties into the 

 San Juan from Costa Rica. Of the tributaries to the San Juan 

 it is second in size to the San Carlos, and, like the latter, bears 



