86 A JOURNEY IN BRAZIL. 



geology, and the almost universal decomposition of the 

 rock surfaces, making it difficult to decipher them. The 

 presence of the drift phenomena, so universal in the North 

 ern hemisphere, has been denied here ; but, in his long 

 walk to-day, Mr. Agassiz has had an opportunity of ob 

 serving a great number of erratic boulders, having no 

 connection with the rocks in place, and also a sheet of 

 drift studded with boulders and resting above the partially 

 stratified metaniorphic rock in immediate contact with it. 

 I introduce here a letter written by him to his friend, 

 Professor Peirce of Harvard University, under the first 

 impression of the day s experience, which will best explain 

 his view of the subject. 



&quot; May 27th, 1865, TIJUCA. 



&quot; MY DEAR PEIRCE : 



&quot;Yesterday was one of the happiest days of my life, and 

 I want to share it with you. Here I am at Tijuca, a clus 

 ter of hills, about eighteen hundred feet high and some 

 seven or eight miles from Rio, in a charming cottage-like 

 hotel, from the terrace of which you see a drift hill with 

 innumerable erratic boulders, as characteristic as any I 

 have ever seen in New England. I had before seen sundry 

 unmistakable traces of drift, but there was everywhere con 

 nected with the drift itself such an amount of decomposed 

 rocks of various kinds, that, though I could see the drift and 

 distinguish it from the decomposed primary rocks in place, 

 on account of my familiarity with that kind of deposits, yet 

 I could probably never have satisfied anybody else that there 

 is here an equivalent of the Northern drift, had I not found 

 yesterday, near Bennett s hotel at Tijuca, the most palpable 

 superposition of drift and decomposed rocks, with a distinct 

 line of demarcation between the two, of which I shall secure 



