In writing of Brazil, Louis Agassiz* says that—
“The decomposition of the surface rocks to the extent to which it takes place is very remarkable, and points to a new geological agency thus far not discussed in our geological theories. It is obvious here . . . that the warm rains falling upon the heated soil must have a very powerful action in accelerating the decomposition of rocks. It is like torrents of hot water falling for ages in succession upon hot stones. Think of the effect, and instead of wondering at the large amount of decomposed rocks which you meet everywhere you will be surprised that there are any rocks left in their primitive condition.”*
By decomposition, decay and disintegration as used in the present paper I refer only to the phase or phases of rock decay which can be detected by the eye. I shall not attempt . . .