THE VALLEnr OF RAU. 



415 



day, we found the bottom of the valley abounding 

 in rieli vegetation, though that was three hundred 

 feet lower than this place, because that valley is so 

 short that the air has no room to l)ecome heated to a 

 dry simoom, which can wither the vegetation as it 

 sweeps along. It is, therefore, in this valley that the 

 simoom is formed, not on the high mountains that 

 border it or on the adjacent ocean. 



March Ist. — Left Rau at 6 a. m., for we have an- 

 other long day's journey before us. As yesterday, 

 the road led along the bottom of the valley, but sooij 

 a range of mountains appeared before us, and we 

 began to ascend along the side of a deep ravine. The 

 rock here was exj>osed, and proved to be a soft sand- 

 stone covered with clay. Here we came to a third 

 water-shed two thousand one hundred and fifty feet 

 high, and coiild look back cloivn the vfUley of Rau to 

 the southeast. Its length in a right line, trom tliis 

 water-shed to that at the gorge near Lubu Sikeping, 

 is thirty geographical miles, but, instead of being 

 straight, it cui*ves to the northeast, and is of a 

 crescent form, ^videst in the middle, and gradually 

 narrowing toward the extremities. In its broadest 

 part it is not more than six or eight miles wide. We 

 now tiimed to the northwest, and began to descend 

 into another valley, that of Mand^ling. Here the 

 mountains are quite devoid of forests, and only cov- 

 ered with a tall, rank, useless grass, the Andropogon 

 caricosum. 



At Marisipongi, the first village we came to in 

 this valley, we found we were among an entirely new 

 people, the Battas or Bataks. They also belong to 



