ments of our scale. A brief review of the possible sources of our supply will find place here, beginning with the lowest and oldest:

The Hudson River Group.

This is, practically, the lowest formation that comes to the surface in the state. There is a single small outcrop of the Trenton limestone at Point Pleasant, and the horizon of the Utica shale is uncovered at a number of localities in the deepest valleys of southwestern Ohio, but if this formation is not entirely lost here by overlap, it has at least been so changed from its typical character and so closely assimilated to the Hudson River series that it is scarcely worth while to attempt to disentangle it from the latter.

The Hudson River group consists of alternating layers of limestone and shale, the relative proportions of which substances vary greatly in different parts of the series. The beds of limestone are available for the manufacture of lime, but the quality of the product is not satisfactory for any but the coarsest uses, as in foundations and road masonry. The limestone when free from the shale contains about ninety per cent. of carbonate of lime. The percentage of magnesia is small, but alumina and oxide of iron occur in proportions large enough to make a dark lime. This last fact is a chief objection to the lime of this formation. Its cementing power is good, and the clay that goes with the stone when burned fresh from the quarries doubtless confers on the calcined product hydraulic quality in addition to that of common mortar, but the product is too dark to allow it to be used with approval in brick-work or in plastering. For the coarser uses, however, as already stated, this "blue limestone" lime is much valued. It is claimed that it makes a more solid and durable foundation, especially in damp locations, than much of the white lime. The claim is very likely a just one.

The composition of the stone in its best phases is seen in the accompanying analysis: (Wormley.)

Carbonate of lime......

Carbonate of magnesia.

91.50 5.06

These figures, however, represent but little of the limestone of the series. The impurities generally constitute not less than eight to ten per cent. of the rock.

Lime production from this series of limestones is not at present of any large importance, and it does not appear likely to become more 80. The stone is harder to burn than those that yield the white limes, and the cost is on this account increased, while at the same time the quality is much less desirable.

The Clinton Limestone.

The Clinton limestone is not the source of a large production, but there are a few counties in which it is now manufactured into a lime of great excellence. Its general composition is indicated in the following figures: (Wormley.)

At a few points in its outcrops, however, it leaves these proportions far behind and becomes the purest limestone that occurs in Ohio. In fact, no purer carbonate of lime is found anywhere, in the large way, than that which the best phases of this formation supply.

lime.

The Niagara Limestone.

In this complex series, there are several subordinate horizons of

The Dayton stone, the place of which is at the very bottom of the Niagara shale, is a limestone of substantially the same composition as that last reported, averaging about eighty-five to ninety per cent. of carbonate of lime, and five to ten per cent. of carbonate of magnesia. It was burned for lime on quite a large scale in the early days of the country, but no account whatever is taken of it for this purpose at the present time.

The series of even beds that occur directly above the Niagara shale and that make the chief reliance of the formation for building-stone, are impure magnesian limestones, selected portions of which yield an excellent hydraulic lime. They are never used in lime production.

The upper division of the Niagara group, which is known as the Guelph or the Cedarville division, is one of the three great sources of lime in Ohio. This division, throughout its whole extent, which reaches a maximum thickness of 300 feet, is in most parts of the state a dolomite or magnesian limestone of great purity and excellence. The following figures indicate its composition throughout its outcrops in southern Ohio. They are derived from an analysis of the best phase of the Springfield limestone: (Wormley.)

The composition of the formation in northern Ohio is equally pure, as appears from the analyses of Lord, to be found on later pages of this chapter. A single one, that of a sample from Genoa, Ottawa county, is given here as fairly representative of a large number:

In this formation, a large amount of stone is found that exactly agrees with the series last described. This phase occurs both in northern and southern Ohio. No analyses are needed to illustrate this statement. The figures that indicate the results of analysis are indistinguishable from those that are derived from analyses of the Guelph. The stone of this character becomes the second of the main sources of Ohio limes. When the formation is not more than 100 feet thick, the whole of it is likely to have the composition above indicated. The lower beds, in particular, are quite sure to agree with the Niagara beds upon which they rest.

A large part of the formation, however, differs very widely from the description given above. Through the northwestern quarter of the state, and particularly in Hardin, Allen, and parts of Hancock counties, the formation consists of a dark and hard phase of the rock that carries along with the dolomite that is its main constituent, a notable percentage of alumina, iron and silica.

The Upper Helderberg Limestone.

This important stratum, which is commonly known as the Corniferous limestone, is the third of the main sources of lime in Ohio. Lime is manufactured from it at Columbus, Marion, Sandusky, Marblehead and Kelley's Island. The stratum contains several subdivisions that differ from one another in chemical composition, growing progressively richer in lime as they ascend in the scale. The lower courses are magnesian limestones, not very different from the Lower Helderberg, on

which they rest. The central division of the formation is represented by the following figures. (Lord.) The composition of the lower beds of the Kelley's Island quarries is given herewith:

This general order is maintained throughout all the exposures of the limestone in the state.

The Sub-Carboniferous Limestone.

The formations already named furnish all of the large supplies of lime in Ohio, but local additions are made from various other horizons. The Ohio shale yields no lime whatever, nor does the Waverly series proper, but a small supply is obtained from the Sub-Carboniferous limestone, which lies at the summit of the Sub-Carboniferous rocks of the state. The lime obtained from this stratum is quite variable in composition, but it is never dolomitic in character. It ranges in composition from seventy-five to ninety-two per cent. of lime and carries comparatively little magnesia, but the silicious and other impurities are extremely variable, and often occur in large amount. The lime production from this horizon nowhere possesses anything more than local importance, and indeed it has but little even of this.

The Coal Measures.

In this great and varied series, as is well known, a considerable number of persistent but generally thin limestones are found. A few of these possess a fair degree of purity as limestones, but the most of them carry iron, alcomina and silica in such large amount as to utterly unfit them for lime production. They furnish natural cements instead, and have been used to a small extent for this purpose.

At various points, however, in the wide distribution of all of these several beds, a higher degree of purity than ordinary is found, and these phases are found adapted to furnace flux and lime production.

The limestones of the Mercer, the Ferriferous and the Freeport horizons, the Cambridge, Crinoidal and Pittsburgh limestones, and the numerous unsteady sheets of the uppermost portions of the series are all occasionally turned to account for one or both of the purposes named. The Ferriferous limestone proper is by far the most valuable of the whole series. Throughout a number of counties in Southern Ohio its character is uniformly good, and it has been the main reliance for furnace flux of an important iron manufacture established here for a long term of years. It is, of course, equally available for lime production. It carries not less than ninety per cent. of carbonate of lime.

The limestones of the Coal Measures are all of the same general character, barring the impurities that they contain. The percentage of carbonate of magnesia in them rarely rises above fifteen per cent., and never reaches dolomitic proportions.

The Drift.

The important series of deposits that compose the drift beds of the state carry a large amount of limestone in the shape of bowlders and gravel. This is especially true in the western half of the state. Where streams have washed away heavy banks of bowlder clay, or where gravel deposits are worked on a large scale, accumulations of limestone blocks derived from all the series to the north of the regions where they are found, are frequently burned in a small way as sources of lime. The lime produced in this way is not likely to be homogeneous in character, on account of the varied horizons from which the bowlders are derived. It sometimes happens that the burning is done entirely beyond the outcrop of the limestone formations, the gravel having been swept in over the Ohio Shales, the Waverly Group, or the Lower Coal Measures.

II. KINDS OF LIME.

In the review that has now been made of the several sources of lime in Ohio, it is seen that limestones of various composition are used in the production at the present time. It is further seen that by far the larger part of our limes is derived from dolomites or double carbonates of lime and magnesia, the approximate proportions of which substances are respectively fifty-four and forty-four per cent. The smaller section includes the limes that are made from stone containing sixty-five to ninety five per cent. of carbonate of lime and five to thirty per cent. of carbonate of magnesia. The higher the proportion of the former element, the more characteristic is the product. The qualities of the limes produced from these two main divisions are well marked, and in several particulars are sharply contrasted. In describing them, these divisions will be known as the magnesian or dolomitic limes and the calcareous limes. The latter designation is objectionable on the score of tautology, inasmuch as calcareous means made of lime, but no other single word is at hand that will indicate the composition of this section, and it seems desirable to avoid a compound term, if possible. Even if willing to