394 
PERU 
CHAP. 
exactly similar appearance, and lying in the same relative 
position. I have no doubt that this upper layer originally 
existed as a bed of shells, like that on the eighty-five-feet 
ledge ; but it does not now contain even a trace of organic 
structure. The powder has been analysed for me by Mr. T. 
Reeks ; it consists of sulphates and muriates both of lime and 
soda, with very little carbonate of lime. It is known that 
common salt and carbonate of lime left in a mass for some 
time together partly decompose each other ; though this does 
not happen with small quantities in solution. As the half- 
decomposed shells in the lower parts are associated with much 
common salt, together with some of the saline substances com¬ 
posing the upper saline layer, and as these shells are corroded 
and decayed in a remarkable manner, I strongly suspect that 
this double decomposition has here taken place. The 
resultant salts, however, ought to be carbonate of soda and 
muriate of lime ; the latter is present, but not the carbonate of 
soda. Hence I am led to imagine that by some unexplained 
means the carbonate of soda becomes changed into the 
sulphate. It is obvious that the saline layer could not have 
been preserved in any country in which abundant rain 
occasionally fell; on the other hand, this very circumstance, 
which at first sight appears so highly favourable to the long 
preservation of exposed shells, has probably been the indirect 
means, through the common salt not having been washed 
away, of their decomposition and early decay. 
I was much interested by finding on the terrace, at the 
height of eighty-five feet, embedded amidst the shells and much 
sea-drifted rubbish, some bits of cotton thread, plaited rush, 
and the head of a stalk of Indian corn : I compared these 
relics with similar ones taken out of the Huacas, or old 
Peruvian tombs, and found them identical in appearance. On 
the mainland in front of San Lorenzo, near Bellavista, there is 
an extensive and level plain about a hundred feet high, of 
which the lower part is formed of alternating layers of sand 
and impure clay, together with some gravel, and the surface, to 
the depth of from three to six feet, of a reddish loam, contain¬ 
ing - a few scattered sea-shells and numerous small fragments of 
o 
coarse red earthenware, more abundant at certain spots than at 
others. At first I was inclined to believe that this superficial 
