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STRENGTH OF THE BRINE.
of the shale, and seemed to show that when this shale was deposited in the state of a fine mud, it was impregnated with salt--probably was at the bottom of a salt lake, liable to be dried up or concentrated by evaporation, and that, when so concentrated, the salt crystallised among the mud in large crystals, as impure salts usually do, and impressed the shapes now seen upon the plastic mud. No solid salt, however, has ever been found in connection with these pseudo-morphic masses. It has no doubt been long dissolved out by rain and spring waters sinking through from above. But while the salt-springs which occur throw light on their formation, these crystals, on the other hand, explain in what way the upper Silurian strata of western New York have in so many places become impregnated with salt.
The wells or borings from which the brine is obtained are sunk in the marshy ground which borders the Onondaga Lake. This lake, which is about five miles long and one mile broad, rests on a bed of impervious marl, beneath which lies a thick deposit of drift, occupying a valley hollowed out of the shales of the salt-group. Into this drift the borings have been carried to a depth of nearly 350 feet; and the supply has generally been more copious, and the water more strongly impregnated with salt, the deeper the boring has penetrated.
If the quantity of salt contained in water which is saturated be represented by 100, that contained in the strongest springs near Syracuse is 76. A hundredweight of salt is obtained from about 700 gallons of seawater ; but of the water from these springs 80 gallons, on an average, yield an equal weight—or 100 pounds of the water yield from 15 to 18 pounds of salt.
It is found, however, that, by constant pumping, the water gradually becomes weaker in salt, and unfit for profitable use; when either the water in that well must be allowed to rest for a time, or new borings must be SALT MANUFACTURED.
put down. This shows that the comparatively freshwater from above, in percolating through the strata of the salt-group to the bottom of the valley in which the drift lies, becomes impregnated with salt contained in these strata ; but no facts have yet been observed which justify any confident opinion as to the actual existence of beds of solid rock-salt in this formation.
The quantity of water pumped up and consumed in the summer and autumn, when the salt-manufacture is most active, amounts to about 2,000,000 of gallons a-day, yielding about 35,000 bushels of salt, weighing 56 pounds each. The total annual production of salt in 1848 was 4,700,000 bushels. The importance of this production of salt, in reference to the consumption and wants, not only of the State of New York, but of the whole United States, will appear, on comparing the above quantity with the importations of foreign salt into the port of New York, and into those of the whole Union respectively, in 1848—and with the whole quantity consumed in the State of New York and by the inhabitants of the United States. Thus there was
Manufactured at Syracuse, 4,737,126 bushels.
1,882,473 Imported into the United States, 8,967,600 ... so that the manufacture at Syracuse is equal to one-half of the entire foreign importation into the States.
As to the relation of the quantity manufactured to the actual wants of the State, it was shown some years ago by Mr Meriam, that the quantity of salt consumed in the United States was at the rate of three pecks (42 lbs.) to each individual. Assuming the population of the State of New York to be 3,000,000, and that of the whole Union 20,000,000, in round numbers, the whole consumption will be
For the State of New York, . 2,250,000 bushels.
188 CONSUMPTION OF SALT IN THE STATES.
Hence the State of New York makes much more salt than is necessary for its own wants; so that, while it imports at New York nearly one-half of its own consumption, it on the other hand exports, by way of the lakes, to Canada and the Western States, about 3,500,000 bushels.
The large alleged individual consumption of salt in the United States is worthy of attention. In ordinary families in Great Britain the quantity of salt used for domestic purposes is about 12 lb. for each individual; and if as much more be used for all other purposes, the consumption ought to amount to 24 lb. a-head, or, in all, to less than 10,000,000 of bushels. But in the United States the consumption is estimated at three pecks, or 42 lb., for each individual—which large allowance, considering there are few chemical manufactories to eat it up, and little is employed for agricultural purposes, appears to imply either a large waste, or an outlet for it which does not exist in this country. It is possible that the large quantities of salt provision which are prepared for home consumption and for export—" the immense packing business of the West,"* as it is called-may be a main cause of the increased proportional use of salt in North America, if the estimate be a correct one.
The salt-springs of Onondaga are the property of the State; and by an article of the Constitution, they and the lands necessary for the manufacture of the salt can never be alienated. The wells are sunk and the water pumped up into reservoirs at the expense of the State, and thence distributed to the various manufactories, for a charge of one cent upon each bushel of salt manufactured. Until the year 1846, the duty levied as a charge for the water amounted to six cents per bushel, and a clear annual revenue was obtained from the springs of about 200,000 dollars.
* In 1848, 34,000,000 of pounds of salted meats, and nearly 3,000,000 of pounds of butter, were exported from the States.
MODES OF MANUFACTURE.
In that year, however, the duty was reduced to one cent, and they now yield a net revenue of about 30,000 dollars a-year. But the production has been largely increased, and the State is greatly benefited in other ways by the reduction. About twelve cents a bushel is now the market price of the Syracuse salt.
The salt is manufactured in three ways: First, by solar evaporation. This is conducted in large wooden vats 184 feet square, and about 12 inches deep, provided with movable lids, by which they can be easily covered in rainy weather. These vats are arranged in long rows communicating with each, and at different levels, so that the water which is put in at one end can be made to flow forward as its concentration advances. The iron is the first constituent of the water which is deposited; after that the gypsum, which forms beautiful small crystals on the bottom and sides of the vats; and then the common salt, in large coarse crystals like those of bay salt—the deliquescent magnesia and lime salts remaining in the waste mother liquors.
The second mode is similar to that followed on our
in large shallow iron pans. The third method is by boiling the water in deep iron pots, or kettles, as they are called, of which forty, built up in two parallel rows, form what is called a block. These kettles are supplied with water from the private cistern of the establishment in which the brine has been purified, by standing some time, or by the addition of quicklime, which carries down the iron, magnesia, and some other impurities. As the water boils away, gypsum first falls in the kettle, and is continually ladled out as it collects at the bottom; and as the liquor concentrates, the salt falls in the form of a fine white powder, which is lifted out, set to drain, and dried. It is then ready for market. This is the favourite and quickest mode; but it makes a less pure salt. About
ORDER OF DEPOSITION OF THE
300 acres are covered with vats for solar evaporation ; and these, in 1848, yielded 713,000 bushels, while only 75 acres are occupied by the blocks, which manufactured
half of the coarse salt is crushed or ground, and sold under the name of dairy salt, being preferred for dairy purposes.
In the order of deposition of the several ingredients of the natural brine in the solar vats, Mr Vanuxem finds a resemblance to, and an explanation of, the mode and order of deposition of the several members of the Onondaga salt-group. “ This group shows first a thick mass coloured red with iron, being its red shale." This corresponds with the oxide of iron first deposited in the vats. “ Above the red shales are the gypseous masses, towards the upper part of which are the salt cavities”—(that is, the hopper-shaped cavities in which crystals of salt are supposed formerly to have existed.) “Above the whole of these deposits is the sulphate of magnesia, its (former) existence there being manifested by the needle-form cavities” in the rock.* This explanation is very natural, and not void of beauty. It may require some modifications to adapt it to the local phenomena in detail—such as the occurrence of the green and blue shales, the limestones, and the calcareous marls. It is, however, neither an unnatural nor unlikely general representation of the probable cause of some of the special chemical characters exhibited by the several successive beds.
A more refined examination of the salts successively deposited in the open wooden troughs in which the water is exposed to spontaneous evaporation might lead to interesting results of another kind. The brine most probably contains both iodine and bromine; and it is possible that, at a certain stage of the evaporation, the saline compounds of
* Geology of the Third District, p. 109.