742 Notice of some Human Remains [August, 
layers of pumice, tufas, marls, volcanic ashes, clays and allu- 
vions. 
In order. to proceed with more certainty in this investigation, I 
compared the calcareous rock in question with those which resem- 
bled it most from other parts of Mexico, and found it could only 
be considered similar to those which are clearly of a hydnotaces 
mal origin. 
The hot-water spring which exists in the eastern part of the 
hill del Peñon- forms sediments somewhat similar to the silici- 
fied calcareous tufa; but these are on a small scale and their 
formation is so slow as to preclude the belief that this spring 
could have filled all the immediate surroundings of the hill with 
deposits of such magnitude. What is most probable is, that in 
remote times there were great emissions of mineral thermal 
waters through different fissures, and in several directions, whose 
appearance was simultaneous with the basaltic masses that form 
dikes at the foot of the hill, as in the faces of the rocks sedimen- 
tations similar to the referred ones are perceived, there being 
furthermore many small veins which cut through the basaltic 
masses and even the calcareous rock. 
By this it is seen that a series of volcanic phenomena must 
have taken place in that spot, beginning before the human remains 
were deposited, and which further continued when the material 
which received them was but little consolidated. 
_ The succession of these phenomena took place, without doubt, 
in the following Way: 
Ist. Emission. of thermal waters and appearance of basaltic 
rocks, upheaving the massés that formed the hill. These waters 
mixed with those of the lake which surrounded the hill and ex- 
tended over a large area of the valley of Mexico; the calcareous 
deposits gradually accumulated around the hill, and being still 
. soft the human corpse was deposited upon them. - 
2d. When the bones were already imbedded in the lacustrine 
deposit there came a new volcanic upheaval which raised this 
deposit, as the higher level which it now occupies proves, and the 
disorder in which the bones of the skeleton appear. 
Got In the gaps which were left after this naeran modern 
oS a trine deposits were formed, which increase even at the priiy 
| — TEIS to he remarked hat in other parts of the valley of Mex- 
