30 DESCRIPTION OF BUILDING-STONES. 
No. 59. Sandstone, from head waters of the Colorado.—This is a very fine-grained red sand- 
stone, resembling in texture and color the red sandstone of New Jersey and Connecticut. It is 
friable, and small fragments may be crumbled in the fingers. 
No. 52. Sandstone, from south side of the Brazos.—This is a fine-grained stone of a light-grey 
color, and sufficiently compact and tough for ordinary building purposes. This specimen con- 
tains a large per centage of carbonate of lime. 
No. 53. Sandstones from head waters of the Colorado.—These two specimens are alike in grain 
and hardness, but differ in color; one is red, and the other grey. They are not very tough, and 
both contain a large portion of carbonate of lime. 
Nos. 56 and 57. Ferruginous sandstone, from between the head waters of the Trinity and the 
Brazos.—These specimens are interesting from the quantity of oxide of iron which they contain. 
The iron oxide appears to be the cementing material, and constitutes the principal portion and 
weight of the specimens. They are both very hard, and are not easily broken, but are not suit- 
able for building purposes. 
No. 69. Ferruginous conglomerate, from near Fort Washita.—This specimen is very rich in 
iron, and, indeed, may very properly be called an iron ore. Its association, however, with the 
silicious sand is not favorable for the manufacture of iron. It is not at all suitable for 
buildings. 
No. 51. Conglomerate, from affluent of the Trinity.—This specimen is interesting, inasmuch as 
the material by which the pebbles are held together is silex. This silex invests each pebble, and 
fills up the spaces between them; it has a semi-opaline character, and in some places successive 
layers on the walls of the cavities are visible, showing a structure like agate. The silex has 
evidently been deposited by the infiltration of silicious water, which has thus produced a hard, 
firm rock. The specimen is a good illustration of the extent to which rocks may be changed 
and modified in their chemical and physical characters by the slow and quiet agency of infiltra- 
tion of water holding foreign substances in solution. 
It is thus evident that a considerable variety is found in the building materials along Captain 
Pope’s route. The light-grey colored sandstones, however, appear to predominate, and are found 
at several points. The specimens of the best quality were from the following places: Guadalupe 
mountains, (where there is also limestone of good quality ;) Llano Estacado, thirteen miles east 
of the Sand-hills, (No.36;) on the east sideof the Pecos, (No. 27;) south side of the Brazos, (No. 
52.) From the Hueco mountains the specimens of granite are very fine, and show that a very 
superior building-stone can be obtained there. It is by far the best building material in the 
collection, and probably can be obtained in any desired quantity. I believe, however, that 
many localities of sandstone will be found at convenient points along the route; and although 
many may not be of the hardest and toughest description, they are sufficiently firm and com- 
pact to endure for long periods in favorable situations. At Fort Belknap building-stone is 
not readily obtained in large quantities at any one point. When the quarters were in pro- 
cess of erection, considerable difficulty was experienced for want of good stone, and that which 
was used was taken from many different places, at a distance of one-half to one mile from the 
post. 
The limestone which occurs a few miles down the river furnishes excellent caustic lime, and 
over 2,000 bushels have been burned there. I judge, from the descriptions, that good building- 
stone could be procured at the quarry. 
The limestone specimens from the Llano do not give much promise; they are not sufficiently 
homogeneous and compact. 
