TOL. LXXVIII.] PHILOSOPHICAL TRANSACTIONS. 371 



giderable depth, and even blew it up in 2 places with gunpowder ; after which, 

 examining the deepest part of the earth, I found it exactly like the upper part, 

 and of the same nature as the earth of all the country, as likewise of 2 pits, 

 which I had dug at the distance of 70 or 100 paces e. and w. of the mass. 

 Finding here no root or trace of generation, I reasoned in the following 

 manner. 



Either this mass was produced in the spot where it lies, or it was conveyed 

 hither by human art, or cast hither by some operation of nature. It could not 

 be generated here, according to any known process of nature. And whence, 

 by whom, or how, could it be conveyed hither, as there are no iron mines 

 within hundreds of leagues, nor remembrance that any have been worked in 

 the kingdom ? It could be of no value, since it could not be used ; and why 

 bring it into a country the most uninhabitable of all the Chaco, from the want 

 of water ? Besides, how could so heavy a mass be conveyed, the Indians never 

 having known the use of wheel carriages ? This mass therefore must have 

 been the effect of some volcanic explosion. Many circumstances induce me to 

 think so. Vblcanos frequently leave behind them, after explosion, pits of waterj 

 either hot or cold ; and at the distance of about 2 leagues to the east of this 

 mass, I discovered a brackish mineral spring, the only one to be found in all 

 this country. In the whole district of the Chaco I travelled over, I observed no 

 difference in the level of the ground, except the very spot where I made this 

 discovery ; and here only I found a gentle ascent running from n. to s. and 

 which attracted my notice before I had seen the mass of iron. This ascent is 

 between 4 and 6 feet above the rest of the country. The earth in every part 

 around this mass, as well as about the brackish spring, is a very light, loose 

 earth, like ashes, even in colour. The grass produced immediately contiguous, 

 called Ahivi, is short, small, and extremely unpalatable to cattle ; whereas the 

 grass found in the rest of the country, at a little distance from the mass and 

 salt spring, is long and very grateful to them. At a little depth in the earth are 

 found stones of quartz, of a beautiful red colour, which the honey-gatherers 

 make use of as flints to light their fires. They had formerly carried some of 

 them away, on account of their peculiar beauty, being spotted and studded as it 

 were with gold. One of these that weighed about 1 oz. came into the hands of 

 the Governor of Santiago del Estero, who told me, that he ground it, and 

 showed me more than 1 dr. of gold that he had extracted from it. 



It is an undoubted fact, that in these immense forests there exists a mass of 

 pure iron, in the shape of a tree, with its branches. Many of the Indians have 

 seen it ; and the inhabitants of the colony of *he Avipones are acquainted with 

 the spot where it lies. A distinguished European of the city of Salta touched it. 

 The body of this tree extends on the ground in the direction from e. to w. 



3 B 2 



