RESUME, 169 
In a practical point of view the Jurassic rocks are rather poor. 
The limestone will furnish lime; the sandstone can be used for embankments and bridges, 
and with some advantage over that of the Trias, for it is harder. Finally, in some locations, 
as at El Ojo Pescado, near Zuiii, in the neighborhood of Fort Defiance, at the cation of Chaca, 
there are beds of bituminous coal in the clay, but only three or four inches thick, so that pro- 
bably they would not be rich enough to be successfully worked. 
Continuing our itinerary, we find that from Anton Chico to near San Antonio we are almost 
constantly on white and yellow Jurassic sandstones. Three miles before reaching San Antonio 
the Trias is met with again, which now is found upheaved and dislocated, the strata dipping to 
the east; and for a space of five miles, all the strata are passed through with the gypsum, dolo- 
mite, Fe 29 and red clay—exactly the same sort of rocks that were seen before in the Trias 
of the prairies. Immediately on leaving the village of Tigeras, which is situated in the middle 
of the pass that crosses the Rocky mountains, called here Sierra de Sandia, and also Albuquer- 
que mountains, black schistose clay is seen, belonging to the coal-measures, then greyish-blue 
limestone, containing a great quantity of fossils. These last beds of schist and limestone are 
very miei upheaved, dipping to the east at an angle of thirty or forty degrees; they rest on 
metamorphic rocks. The principal fossils found in the limestone which belongs to the mount- 
ain limestoné or lower carboniferous, are the Productus semireticulatus, punctatus et flemingi, the 
Spirifer striatus et lineatus, Terebratula, Crinoids and Corals, which are all fossils very charcter- 
istic of the mountain limestone of Arkansas, Missouri, Iowa, Illinois, Indiana, Kentucky, Ten- 
nessee, Virginia, and Pennsylvania, as well as in Europe, and even in Australia and South 
America. 
We have not met upon our route with beds of coal; but the presence of the black slate between 
the mountain limestone and the red clay of the Trias, indicates the existence of beds of coal on 
several points of the Rocky mountains ; and, indeed, the inhabitants of New Mexico pointed 
out to me, in several places, beds of bituminous coal belonging, without any doubt, to the rocks 
of the coal measures. 
[ v itting the last beds of limestone that rest upon the quartzose metamorphic rocks, we 
rpentine ; then we come upon masses of granite, somewhat sienitic, which form the centre 
of the line of dislocation of the Rocky mountains. After going through the pass, which is 
fifteen miles long, we come out in the plain of the Rio Grande del Norte, where the granite is 
found covered with drift and alluvium, which form the whole plain as far as the right bank of 
the river, where the formation is sandstone. This sandstone is white, friable, horizontal in 
stratification, and forms almost the whole of the bottom of the valley which lies between the 
Rocky mountains and the Sierra de Jemez, and Mount Taylor or Sierra de San Mateo. On 
some points, as at Galisteo, it is covered by a greyish schistose clay, containing nodules of iron 
and numerous plaquettes, composed of the scales and fragments of bones of fishes, belonging to 
the genus Péychodus. In this sandstone and clay, which rest horizontally on the upheaved beds 
of the Trias, the Jurassic and the Carboniferous, are found the remains of Ammonites, Scaphite, 
Inoceramus, and the Péychodus, which indicates, for the relative age of this formation, the creta- 
_ceous group, and, further, the white chalk of Europe. This fact is a new one in the geology of 
1 America, where, until now, the true chalk has not been recognised ; and now the cretaceous is 
here found to be composed of four divisions, precisely as in Europe: the neocomien, which I have 
found on the Canadian, the False Washita, and at Fort Washita: the green-sand of Timber 
creek, near Philadelphia; the marly chalk of Bordentown, New Jersey, of the Bad Lands, Ne- 
braska, and of Fort Washita; and finally the white chalk, or craie blanche, of New Mexico. 
Besides, the discordance of stratifiontion of the upper cretaceous of New Mexico, with all the 
sedimentary rocks found there, indicates that this formation was deposited after the principal 
dislocation of the Rocky mountains, which took place at the end of the American Jurassic period. 
From the Rio Puerco to the Sierra Madre, our route was constantly upon beds of Trias and 
Jurassic, which are often covered in this region by immense overflowings of lava, coming from 
22 
