ROCK DECOMPOSITION 69 



At Pirangy (kilometer 129 ; elevation, 120 meters) the residual earths 

 are of a deep red color with yellow and purple streaks. Two and a half 

 kilometers west of Pirangy is a cut 12 meters deep in decomposed crys- 

 talline rocks. 



At and immediately west of Boa Sorte (kilometer 133.5 ; elevation, 

 125 meters) the cuts expose decomposed schists with the residuary earths 

 of strikingly brilliant colors — red, white, yellow, and purple. 



In the rear of the station at Jaqueira is a cut in yellow and reddish 

 yellow earth. One kilometer east of Colonia are deep cuts in decomposed 

 crystalline rocks. The earths are highly colored. 



At Florestal (kilometer 167.8 ; elevation, 246 meters) there is a cut 

 12 meters deep in decomposed schist-like rock. The rocks at the bottom 

 of this cut are not decomposed. 



Just west of Barra da Jangada station (kilometer 174.7; elevation, 

 296 meters) is' an 8- meter cut in decayed crystalline (schistose) rocks. 

 A hundred meters east of Pery-Pery station decayed crystalline rocks 

 are cut. One hundred and fifty meters farther west there is another cut 

 10 meters deep. 



West of Sao Benedicto there are several deep cuts nearly all of them 

 in decomposed rocks. West of Quipapa several cuts in decomposed 

 rocks expose kaolin, but the residuary earth is mostly of a red color. 

 On the watershed west of Agua Branca the railway cuts are from 12 to 15 

 meters deep in decomposed rock cut by quartz veins ; the residuary earth 

 is highly colored, and shows marked bedding or the foliated structure of 

 schists. At Glycerio * (kilometer 214 ; elevation, 529 meters) there is 

 a cut from 9 to 12 meters deep in decomposed crystalline schists. This 

 rock was faulted before it decomposed. The residuary earth is mostly 

 of a purplish color. 



STRUCT URA L FEA T URES 



Returning to Cabo, we may now consider the nature and structural 

 features of the rocks exposed along the line of this railway. From Cabo 

 west and south the road passes over crystalline rocks nearly all the way 

 to Garanhuns, a total distance of 240 kilometers. These rocks seem to 

 be granites, gneisses, and schists, but under the circumstances of pro- 

 found decomposition in most cases and lack of opportunity for careful 

 examination in others, nothing more than impressions can be set down 

 for many of the exposures. Wherever it was possible to observe it, the 

 approximate direction of the strike of the beds was noted. 



Between Timbo Assti (kilometer 51.8) and Escada (kilometer 57.6) 



* At this place the connection is made with the Alagoas railway to Maceio. For notes on the 

 geology of that line see Proc. Wash. Acad. Sci., vol. ii, pp. 195-201. 



