>9i3.] OF GRANITES IN THE TROPICS. 167 



vertical or nearly so, but some of them are also nearly horizontal. At 

 Quixada they are more abundant on the gentler slopes and especially 

 about the bases of the hills. In Plate V., Fig. B, for example, there is 

 a striking difference between the fluted surface in the upper part of 

 the hill and the pitted and fluted surface of the rock about the base 

 of it. 



The great rock in the edge of the village of Quixada is a striking 

 illustration of the combination of pits and of fluting, though the 

 caldrons are the more marked feature of this particular mass (Plate 

 VI., Fig. B) . The photographs of Itatiaya show the surface to be 

 pitted here and there, but the pits appear to be formed on vertical 

 walls as well as on sloping or flat surfaces (Plate VII., Figs. B, C). 



A good deal has been made of pits or pot-holes in the granites in 

 other parts of Brazil. In Hartt's " Geology and Physical Geography 

 of Brazil," at pages 314-315, is an account of holes observed in 

 granites in the interior of the state of Bahia. Following are the 

 notes of J. A. Allen on the region southeast of the Serra de Jacobina. 



" At frequent intervals there were singular holes in the rocks, usually 

 nearly filled with water, to which the inhabitants give the name ' caldeiroes.' 

 These ' caldeiroes ' are of frequent occurrence, but I was unable to learn 

 whether all were of a similar character. Nearly all of the considerable num- 

 ber examined proved to be genuine pot-holes, and some of them were of great 

 size. The largest one I measured was elliptical in outline, eighteen feet long, 

 nine or ten in width, and twenty-seven deep, with smoothly worn sides. Be- 

 neath the water that partially filled it there must have been many feet of 

 materials that for ages have been falling into it, so that its whole depth must 

 be much greater than my measurements indicate." 



Professor Hartt adds the following as a footnote : 



" Mr. Allen tells me that these pot-holes often occur out on the plain, far 

 away from any high land, and that they are sometimes found excavated in 

 the summits of slight bulgings in the plain, or even on the top of a hill, as in 

 the case of the Morro do Caldeirao. These holes must have been excavated 

 by falling water. There is only one suggestion that I can make as to their 

 origin, and that is that they were formed by glacial waterfalls, in the same 

 way as the pot-holes found over the glaciated regions of North America, as, 

 for instance, in New Brunswick and Nova Scotia, where I have had an oppor- 

 tunity of examining them. It is well known that glacial waterfalls, notwith- 

 standing the constant movement of the ice, are very often stationary, and 



