16 



AUTOBIOGRAPHICAL NOTES. 



underlying rock is gneiss, with vast exposures of bare rock, and with nowhere 

 more than a very thin covering of soil. Slight knolls and shallow basins 

 alternate, with rarely a difference in altitude of more than twenty or thirty 

 feet. Many of the hollows form shallow lakes in the rainy season, from 

 which most of the water evaporates in the dry season. At frequent inter- 

 vals there are circular holes in the rock, called by the natives caldeiraos, 

 which I found on examination to be genuine pot-holes, some of them of 

 great size (the largest one measured was 20 feet in diameter). 



A considerable descent is made in passing from the middle to the eastern 

 or coast plateau, which is characterized — at least along our route of travel 

 — by the general absence of rock exposures and heavy superficial deposits 

 of sand, doubtless from the abraded plains to the westward. The whole 

 region between the Sao Francisco and the sea is covered, generally speaking, 

 with low open forest, or catinga, except for a narrow belt along the coast, 

 where a moister atmosphere permits a more luxuriant growth. The whole 

 area presents a barren aspect, the vegetation being dwarfed and scanty and 

 the aridity excessive. The greatest aridity and the highest temperature 

 occurs in the limestone district, where little or no moisture is precipitated 

 for nine months in the year, and where all the herbaceous vegetation an- 

 nually withers. Cacti occur in great variety, including arboreal forms of 

 gigantic proportions. With the exception of a few species, the trees are 

 leafless throughout the long dry season, and the streams become dry or 

 merely form chains of brackish pools. 1 The convolvuli and other vines 

 clinging to the arboreal vegetation, though dead at this season, indicated 

 the presence of a wealth of flowers and foliage during the short rainy period. 



Our train comprised several score of pack mules and a considerable num- 

 ber of riding horses. Eight animals were necessary for the transportation 

 of my collections. The journey occupied several weeks of rather tedious 

 travel, Bahia not being reached till about the end of November. I soon 

 found storage in a warehouse for my collections until I could arrange for 

 their shipment to Boston. They included several cases of bird and mammal 

 skius, mollusks, and geological specimens, besides some six or eight barrels 

 of fishes, reptiles and other vertebrates in alcohol. These required repack- 

 ing for shipment, new casks being necessary for part of the alcoholics. 

 Some days later, I found that my fine work in repacking was only temporary, 

 for at the custom house an export duty of 8^ per cent was levied on natural 

 history specimens, which involved the opening of my cases for inspection! 

 As I knew Professor Agassiz had an agent, who was also a warm personal 



1 1 found the water at midday in some of the trickling streams we crossed had a temperature of 

 102° F. 



