96 AGRICULTURAL REPORT. 
purposes to which it is generally applied. The above constitution shows 
it to contain 75 per cent. of pure crystalline gypsum, 6 per cent. of inter- 
stitial water, and 18 per cent. of impurities. 
Dr. Edward Palmer brought to the laboratory from Western Kansas 
prairies a sample of what is called “alkali” of the western plains. It 
was in the form of a dry, milk-white powder, mixed with bleached 
leaves and coarse grass. It did not effervesce with acids, nor did it 
exhibit an acid reaction to test-paper. It contained: 
VA! . scp aes ee Reese Ree < wnt = bacce co ccs wee pee meeinbe es sc ses pee 3.6 
qnsoluble Clay ieee per eeec sc occs sou sas ae mone «seer ae ee eee 15 
Cliloride OfqseatiI 92. toca Sa seo acs coe esa tee cin b et eae Cee es ae ee eee traces. 
0) PHO UO NE PGE ee memes ale 6 ac = San) fas Sa a od eee ee ee eee 94.6 
99.7 
It is consequently a native sulphate of soda, which, from the small 
amount of water present, may be classed as anhydrous. There is no 
evidence to show that it is a product of volcanic action. It differs from 
the varieties of mirabilite of Dana in the small amount of water, which 
we may conjecture has been lost during the prolonged heat of summer. 
It may owe its origin to the decomposition of sulphate of lime, which 
is so largely present in the soils at the foot of the Rocky Mountains and 
Sierra Nevada series, by means of carbonate of soda occurring as 
efflorescences on soil. The usual origin of sulphate of soda is either 
directly from volcanic sources, or by the delivery of springs containing 
the salt derived from preéxisting sedimentary beds. In a few cases it 
is derived from the oxidation of sulphur in bituminous strata, or in 
pyritiferous beds, which, reacting on common salt, produces thenardite 
or other forms of sodic sulphate. 
MARLS—THEIR USE AND INFLUENCE. 
There is no class of substances which is more frequently examined 
in this laboratory than the marls found in the several States. Hundreds 
of them are constantly being forwarded. It would be unnecessary to 
swell the report with returns of their composition, although to the 
different States there could be no contribution of greater value to their 
agriculture than a thorough examination and report upon the extended 
marl] beds, mineral deposits, and sources of lime for agriculture. Science 
now no longer looks on marls and similar deposits as merely such a 
weight of earthy materials, composed of a certain number of hundred- 
weight of sand, or so many pounds of lime, magnesia, and oxide of iron, 
added to the soil to directly increase the amounts of these substances ; 
but also as composed of substances possessing physical properties and 
chemical affinities whereby they react upon the farm-yard and other 
manures, when brought into contact with them, and become detainers 
for a more or jess lengthened period of some of the richer portions of 
the compost heap, and prevent their removal from or loss, to the soil by 
the washing influence of rains. If this did not occur we should never 
find ready formed ammonia and nitric acid in all fertile soils, and 
soluble chlorides and sulphates which are afterward found in the ashes 
of plants. The experiments of Professor Way are well known, in which 
he proved the power of soils to absorb and retain mineral matters in 
solution, and to deprive a solution of a certain percentage of its saline 
matters. In passing a solution of ammonia through several soils, he 
found that all soils had the power of retaining a portion of that body, 
some more and someless. He also observed that lime, magnesia, potash, 
