Cb. III.] REACH THE LAKE. 35 



some of the black Congo monkeys (Mycetes pattiatus) 

 which at times, especially before rain and at nightfall, 

 make a fearful howling, though not so loud as the 



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Brazilian species. Screaming macaws, in their gorgeous 

 livery of blue, yellow, and scarlet, occasionally flew over- 

 head, and tanagers and toucans were not uncommon. 



Twelve miles above Castillo we reached the mouth of 

 the Savallo, and stayed at a house there to breakfast, the 

 owner, a German, giving us roast wari, fowls, and eggs. 

 He told me that there was a hot spring up the Savallo, 

 but I had not time to go and see it. Above Savallo the 

 San Juan is deep and sluggish, the banks low and 

 swampy. The large palm, so common in the delta of 

 the river, here reappeared with its large coarse leaves 

 twenty feet in length, springing from near the ground. 



Our boatmen continued to paddle all day, and as 

 night approached redoubled their exertions, singing to 

 the stroke of their paddles. I was astonished at their 

 endurance. They kept on until eleven o'clock at night, 

 when we reached San Carlos, having accomplished about 

 thirty-five miles during the day against the current. 

 San Carlos is at the head of the river, where it issues 

 from the great Lake of Nicaragua, about one hundred 

 and twenty miles from Greytown. The mean level of 

 the waters of the lake, according to the survey of Colonel 

 0. \Y. Childs, in 1851, is 107^ feet, so that the river 

 falls on an average a little less than one foot per mile. 

 The height of the lowest pass between the lake and the 

 Pacific is said to be twenty-six feet above the lake, 

 therefore at that point the highest elevation between the 

 two oceans is only about 133 feet; but even allowing that 

 an error of a few feet may be discovered when a thorough 



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