ORIGIN OF BEDS OF GYPSUM. 85 
the country. It is even taken in quantities from the sea-board, by railway, far into the interior, 
to the broad fields of northern Virginia, situated on the new red sandstone or ** Trias." Some 
idea of the extent to which this substance is used in agriculture may be obtained from a know- 
ledge of the amount taken from the quarries of Nova Scotia and New Brunswick, and exported 
to the United States in 1851. This, according to Mr. Andrews, was 40,592 tons, and valued 
at $28,145. Andin the year 1850, the quantity quarried reached the enormous amount of 
79,795 tons. According to Dawson, the quantity quarried in Hants and Colchester districts 
in 1851 was 78,903 tons, having a value of £10,000 at the ports of shipment, the greater part 
of which is exported to the United States for agricultural purposes.? 
It is thus seen that there is an immense and inexhaustible supply of this valuable mineral in 
convenient proximity to all parts of the Atlantic coast of the United States. It is readily 
quarried at little cost, and can be loaded directly into vessels without land transportation. 
This is sufficient to show that the deposits of Texas and New Mexico cannot become valuable 
as a source of gypsum for export. The expense of quarrying in horizontal beds is greater than 
in vertical ones, where they are exposed in bluffs; and the distance of the Texas deposits from 
seaports will confine the use of the gypsum to its immediate vicinity. 
Origin of the gypsum beds.—The origin of these great beds of gypsum has excited much 
speculation, and numerous hypotheses have been formed by different writers to account for their 
formation. Some suppose the thick beds to have a mechanical origin—they having been depos- 
ited at the same time with the adjoining strata, and in a similar manner. Their igneous origin 
was formerly advocated—the absence of stratification in some beds being regarded as evidence 
of their once melted or fluid condition, and of their intrusion between the strata, as volcanic 
rocks or lavas are found to traverse stratified deposits. The doctrine of the chemical character 
or origin of the deposits is now, however, very generally accepted. Although not now pre- 
pared to enter into a full investigation and consideration of this difficult subject, I would re- 
mark, that when in California, in 1853, I was led to some conclusions respecting the formation 
of gypsum beds, by the study of phenomena presented in the Tertiary strata of Ocoya or Posé 
creek, where beautiful seams of transparent and fibrous gypsum occur. 
Veins and layers of oxide of iron, produced by infiltration, are found at that place; also 
large beds of the same substance where there had formerly been accumulations of fossils, their 
casts only being left in the firm oxide, while all the lime had been removed. Still further 
below we find layers of crystalline gypsum, presenting in their structure full proof of an origin 
subsequent to the deposition of the strata. These conditions were evidently the result of the 
infiltration of acid waters downwards through the strata; the lime of the shells having been 
dissolved, and a simultaneous deposition of iron produced. 
Iam inclined to regard all the great beds of gypsum of the Gypsum formation underlying 
the Llano as formed by the percolation through the strata of water charged with free sulphuric 
one of the most curious features of the mine. On close examination, it appears to be laminar and concentric, and to con- 
sist of layers of blue clay and gypsum. Now the whole formation of gypsum contains a small portion of clay, which gives 
it the greyish color ; and it is probable that when that peculiar principle, whether crystallization, attraction, et electricity, 
which caused the aggregation of the particles of gypsum in greater purity and in a more crystalline state was in o on, 
one of its chief effects was to expel to the circumference all the particles of argillaceous matter previously mixed up with 
the gypsum; a process which would continue until either the crust itself opposed a resistance to the further action of this 
principle, or until two opposing spheres nearly came in contact with each other.”’ j 
‘t Very fine crystals of selenite, and sometimes of a large size, are not unfrequently found in the fissures of the gypsum. 
They are used for the purpose of making the fine scagliola cement, and are consequently sold at a much higher price than 
the ordinary gypsum. The price of the fine alabaster is 5 Tuscan lires the 100 Ibs. Tuscan at the quarry, or 8 if delivered 
in Leghorn."  [Quart. Jour. Geol. Soc. Lond. vol. i, p. 282.] 
t Andrews's Report on the Colonial and Lake Trade : Washington, 1854, pp. 491 and 493. 
? Acadian Geology, p. 238. 
3 Other interesting facts and observations upon the gypsum will be found in detail in the writer's forthcoming report of a 
