CHAP. V. THE BASIN OF 3IACIIACHI. 105 



divided from one another almost as sharply as in the section upon 

 p. 104, and each evidently belongs either to a single eruption, or 

 period of eruptions. 



Machachi is situated^ towards the bottom of a basin measur- 

 ing about twenty -one miles from north to south and eleven 

 from east to west, which is bounded on the north by the Tam- 

 billo ridge (a modest eminence connecting the lower slopes of 

 Atacatzo with the Puengasi ridge), on the south by the Tiupullo 

 ridge, on the east by Kuminahui and Pasochoa, and on the west 

 by the north-eastern slopes of Illiniza, Corazon, and the south- 

 eastern slopes of Atacatzo. The elevation of this area is greater 

 than the basins of Latacunga or Riobamba, and with the excep- 

 tion of its north-east corner it is everywhere more than 10,000 

 feet above the sea. The drainage of the basin is collected into 

 a small stream called the Rio Grande,^ which passes to the east 

 of the Puengasi ridge, and ultimately falls into the Pacific at 

 Esmeraldas. The high road to Quito ^ runs very directly across 

 the bottom of this basin, falling slightly the whole way from 

 south to north, as far as the little cluster of houses called Tam- 

 billo, where the ascent of the ridge of the same name commences ; 

 and, when this is passed, the basin of Quito is entered, and the 

 road again falls continuously towards the capital. 



Illiniza, Corazon, Atacatzo, Pasochoa, and Rumifiahui stand 



^ The tambo and a long line of straggling houses are upon the high road, but 

 the town (or village) proper of Machachi is about three-quarters of a mile to the 

 east. The entire population amounts perhaps to 2500 persons. 



2 Where we crossed it on our way to Pedregal it was not more than two feet 

 deep and fifty across. It was frequently remarked that the volume of water in 

 the streams was exceedingly small, considering the areas drained by them. This 

 is no doubt due to the soil being greatly fissured. In December, I walked across 

 the Chimbo at Guaranda from stone to stone without wetting my feet. The bridge 

 seemed dangerously low, but I was informed by the authorities that it was never 

 in risk of being carried away, although the rainfall there, as well as in the in- 

 terior generally, was considerable. 



^ In Jan., Feb., and June I measured 22,385 feet where it runs across the 

 plain. The measurement extended from the most northern house of Machachi to 

 the fine bridge of Jambeli, the largest structure of its kind I saw in Ecuador. 



