DESCRIPTION OF THE COLLECTION. 113 
tals have curved surfaces, and some of them are pearly, and resemble the pearl spar found with 
the gypsum of Lockport, New York. 
No. 74. Comet creek.—A fine specimen of white, amorphous gypsum, very compact and solid. 
The mass appears to have formed part of a layer one and a half inches thick, as it has a strati- 
fied character, and has two broad, flat surfaces parallel with the layers, and stained as if they 
had been in contact with grey or blue marl, or clay. Mr. Marcou marks this specimen as from 
the Middle Trias, (** Trias moyen.’’) 
No. 75. Comete creek.— White saccharoidal gypsum, amorphous. It is slightly stained with 
red. From the rr Trias moyen,” according to Mr. Marcou. 
No. 76. ‘Prairie near Gypsum creek.— White fibrous or plumose gypsum. This is apparently 
part of a layer about two inches thick, and it has in the middle a divisional seam from which 
part of the fibres radiate, and which contains a thin layer of greenish shale. 
No. 77. Gypsum creek.—Opaque, amorphous gypsum, with a grey or reddish white color and 
fine grain. One side of the specimen is composed of greenish grey shale or clay, which is 
traversed by irregular seams or veins of gypsum, that are connected with the principal mass. 
It appears to have been imbedded i in the blue clay, both faces of the specimen being covered 
with it. > 
No. 78. —— ?—This E is without a label. It consists of compact amorphous 
gypsum of a flesh-red color, and containing patches of blue shale, as in the preceding, It is 
probably from the same locality. P 
No. 79. Grande prairie, Camp «No. 30.—A white amorphous gypsum, stained with red veins. 
The mass is slightly porous or cellular, and somewhat resembles No. 75. 
No. 80. Camp 30.—This is similar to No. 79, and is probably from the same bed. 
No. 81. Camp 30.—A plate of selenite, surrounded by amorphous gypsum veined with rea 
«It is probably from the same bed as the preceding. 
No. 82. San Antonio.—A. white granular gypsum, with a pleasing crystalline grain resembling 
some fine-grained marbles. It is white, solid, and compact. This is from the ** Trias,’’ accord- 
ing to Mr. Marcou. 
No. 83. Cajon Pass, (from the Great Basin to San Bernardino. )— White or reddish white sand- 
stone, composed chiefly of feldspar and quartz, with some mica. It has resulted from the abrasion 
of granite and the allied rocks. Its red color is due to the presence of a large amount of pink 
feldspar. The specimen is interesting, as almost the only one in Mr. Marcou’s collection, which 
he has labelled as from the Tertiary or Quaternary formations. It is also interesting from the fact 
that the cementing material—carbonate of lime—is beautifully crystallized, so that the whole 
surface of the specimen is covered with brilliant reflecting surfaces, seen only when it is held in 
certain positions. Viewed in some directions the crystalline character of the specimen is 
invisible, or would not be suspected. This crystallization of the mass enveloping the grains of 
sand is like that of the Fontainebleau sandstone. 
No. 84. Camp before Cactus Pass.—Mr. Marcou considers this specimen as Quaternary, and 
observes, on the label, that it was covered with the lava of a volcano. It is a conglomerate of 
rolled masses of pumice-stone and small pebbles and sand, the cementing material being appa- 
rently fine volcanic ash, or the fine dust from the abrasion of the pumice. I have found similar 
agglomerations under the basaltic lava near Fort Miller, on the San Joaquin, and in the Ter- 
tiary or Quaternary deposites of Ocoya creek, California. 
No. 85. ‘‘ Little stones, of which the ants build their mounds, west of the Sierra Madre." — 
These little grains or pebbles are very uniform in size, and are, nearly all of them, over one- 
eighth of an inch in diameter. "Transparent grains of quartz are very numerous, some of them 
retaining a part of the planes of crystallization. "The remainder of the grains consist chiefly of 
carnelian, chalcedony, and hard volcanic rocks. Fragments of granite are also numerous. 
These grains are entirely free from sand or dust, and are remarkable for their uniform size and 
Sean, 
15 1 
