A rock of this character will make an excellent fertilizer for many soils, but it would not be profitable to grind it here where the better grades are equally available.

The composition (in part) of the blue limestone that is found between divisions two and three (No. 1), and of the shaly envelope by which the plaster bowlders are covered (No. 2) are also given herewith. They are constituted as follows: (Lord.)

A careful search was made for fossils in the limestones that include the plaster beds, but none were found. The conditions would necessarily be unfavorable to all forms of life, where beds of gypsum were in process of formation.

As to the origin of these accumulations through northern Ohio, all the facts point to deposit from a shallow, land-locked and contracting sea during the Lower Helderberg period. The first deposit from such a sea, undergoing concentration, is sulphate of lime, either in the form of gypsum or anhydrite. The latter form is very often found in connection with beds of rock salt, immediately underlying them as a general rule. At only one point in northern Ohio, have beds of rock salt been reported in this series, viz., at Newburg, near Cleveland. The facts pertaining to the salt discoveries there are given on page 352.

The shallowness of the sea in this period is well established by the sun-cracks and wave-marks that are so conspicuously shown in the rocks that represent it throughout their outcrops in this part of the state. That the sea must have been land-locked or cut off from free communication with the main ocean is also an obvious deduction from the concentration of the sea-water that went forward.

The facts pertaining to the gypsum deposits now under consideration were given by Newberry, Geol. of Ohio, Vol. II, page 135, and valid conclusions were drawn by him as to the mode of origin of these deposits. He urged the views presented on the previous page, and showed the unsatisfactory nature of the alternative explanation, viz., that beds of gypsum are due to the action of the waters of acid springs on beds of carbonate of lime. The wide-spread discoveries of deposits similar to those of Ottawa county in the deep wells that have been drilled in such numbers throughout northern Ohio during the last three years, reinforce and sustain this view in a very effective way. The acid-spring theory, no one would be bold enough to urge as an explanation of deposits that are measurably continuous over thousands of square miles of territory.

COMPOSITION AND USES.

The gypsum produced by the quarries now under consideration is devoted to two main uses, viz., calcined plaster or stucco, and land-plaster. About forty per cent. goes to the first product, and sixty per cent. to the latter. The total value of the calcined plaster considerably exceeds, however, that of the land-plaster. Under this latter division, the dental plaster, the glass-works plaster, and also the terra alba of the works is counted.

The calcined plaster of Marsh & Co.'s production is recognized in the markets as of great excellence and purity. Its reputation is fully sustained by the following analysis, made from an average sample of the output of the quarry: (Lord.)

The best stone of the quarry goes into this division. All, that is streaked with shale or from any cause "off color," is turned into landplaster. Into this division is also put all the surface stone which is known as "rotten plaster." The latter is somewhat stained by surface infiltration, but chemical analysis shows that it has lost nothing of value. The figures are as follows: (Lord.)

Evidently the sample tested belongs to the best product of the

quarry.

The analysis of the land-plaster in like manner shows the great excellence of the entire product of the quarries, and the slight differences that separate the two divisions which are made of it. It is as

A small amount of the purest stone, and mainly derived from the bowlders previously described, is supposed by the manufacturers to be used as terra alba. The main applications of this form of gypsum are in mischievous adulterations. The calcined plaster reaches the general markets of the country as far east as Pittsburgh and Buffalo, and to the southward indefinitely. The land-plaster is largely used in Michigan. Ohio farmers have been slow to avail themselves of this excellent fertilizer. About 6,000 tons are used annually by glass manufacturers. The production of these quarries is specially adapted to this demand. PRODUCTION.

The production of the quarries and works for the last few years are shown in the following table:

The works are now in excellent condition, having been rebuilt in 1885. (This fact accounts for the small production of that year). The mills were previously located at the railroad, nearly a mile distant from the quarries, and large expense was incurred in hauling the stone to the mills, but now a railroad switch runs in to the quarries and excellent facilities for hauling the stock and loading the product have been secured.

The works will allow an easy expansion to meet an enlarging demand. There is enough proved gypsum to keep the mill in operation for a considerable term of years, and there is good reason to believe that when proper exploration shall be undertaken, large accessions will be made to the acreage already known.

An attempt was made by Marsh & Co., in 1885, to introduce the roller process for grinding the rock, but the experiment proved unsuccessful, and a return was made to the time-honored method.

The water that fills the quarries to the lake-level, unless kept down by the pump, is a strong sulphur water, carrying a notable quantity of sulphuretted hydrogen. The source of this product is probably to be found in decompositions of the gypsum of the rocks through organic matter carried downwards by surface waters. Such an origin is possible, at least. The oxidation of the sulphuretted hydrogen gives rise to sulphuric acid which produces an acid re-action in the water, rendering it unfit for boiler use.

CHAPTER XV.

THE PRODUCTION OF LIME IN OHIO.

BY EDWARD ORTON.

The production of lime is an important and growing interest in Ohio. Lime is burned in the large way, and generally for railroad or lake shipment, from stone quarried on the spot, in the following counties of the state. The enumeration is begun in the southwestern quarter:

To this list Cuyahoga county may be added, as a large amount of lime is burned here from stone brought in by the lake from Marblehead and Kelley's Island.

In twenty or more other counties, lime is burned for local use or even for occasional shipment, but there are no important centers of production within them at the present time. In several of the counties in this last group, the conditions for a large production are found, so far as limestone of desirable quality is concerned, but they do not command equal advantages with the counties of the first list in the matter of transportation and markets.

All of the large production comes from the western half of the state. In forty-two out of fifty counties that make up western Ohio there are limestone quarries available from which lime of greater or less excellence can be produced.

I. GEOLOGICAL HORIZONS.

To name the several geological formations from which lime is or can be burned in Ohio, requires the enumeration of almost all the ele