have yet been found. The 340 feet of limestone underlying the shale, represent the Guelph, Niagara and Clinton formations, and the red and blue shales beneath these belong to the Medina formation. By referring to the account of a boring at Barton, near Hamilton, it will be seen that these shales have there a total thickness of about 600 feet. (Report for 1866, page 251.) It will be noticed that the Onondaga formation, as shewn in the borings of Goderich and its vicinity, consists of several hundred feet of limestone, chiefly magnesian, underlaid by two or three hundred feet of red and blue shales, which carry rock-salt at their base. These are succeeded, in descending order, by the magnesian limestones of the Guelph, Niagara and Clinton formations, which rest upon the red shales of the Medina, as seen in the Southampton and Waterloo borings. We have the following succession in going downwards: 1. Limestones of the Onondaga or Salina formation.; 3. Limestones of the Guelph and Niagara formations. On account of the resemblances in color between the upper and lower couples of the above series mistakes may easily occur, as at Southampton, where the strata of 3 and 4 were supposed to be those of 1 and 2. Such errors, which have caused the expenditure of considerable sums of money at Southampton, Port Elgin, and Waterloo, would be avoided by a careful study of the distribution of the various geological formations of this region, as described in the Geology of Canada. The accuracy with which the limits of the various formations throughout this region were traced out by Mr. Alex. Murray, has received repeated confirmation in the course of the various explorations for oil and salt which have been made within the past few years. As regards the possible extent of the salt-bearing area now under consideration, I take the liberty of quoting the following passage from my Report for 1866, page 271: With regard to the probabilities of obtaining salt wells by other borings in this region, it is to be remarked that the thickness of the deposit of salt traversed in the Goderich well may warrant us in expecting that its area may be considerable; though whether its greatest extent will be inland, or beneath the waters of the lake, can only be known by experiment. It has already been explained that salt deposits have been formed in basins whose limits were determined by the geographical surface at the time; and it is worthy of remark that both here and in New York the salt deposits are connected with a thickening of the Onondaga formation, which, in its thinner intermediate portion, is apparently almost destitute of salt; a fact suggesting former geographical depressions, in which the two salt bearing portions of the formation may have been deposited. Although it would be unsafe to predict that this development of salt at the base of the Onondaga formation is so widely extended, its thickness at Tilsonburg, St. Mary's, London, and Enniskillen, is such, that it seems probable that farther borings in these localities, where deep wells have already been sunk, may reach saliferous strata capable of yielding valuable brines." In confirmation of the first portion of the above extract, we can now point to the existence of salt at Clinton, thirteen miles to the S.E., and at Kincardine, thirty miles N.N.E. of Goderich. These two stations are forty miles apart, and a line connecting them would pass about seven miles to the east of Goderich. It is, therefore, extremely probable that the whole region between Clinton and Kincardine will be found underlaid by salt, and may belong to a single basin, whose extent yet remains to be ascertained. The success of the borings at Goderich and in its vicinity has, as we have seen, led to the sinking of wells for brine, below the salt-bearing horizon. At the same time, other trials have been made in the hope of reaching it, by boring through rocks overlying those of the Goderich region. For the information of inquirers, it may therefore be well to recall briefly some of the facts with regard to the nature and thickness of these rocks, of which the details are given in my Report for 1866. It will there be seen that the most recent rocky strata in south-western Ontario are the greenish sandstones of the Portage formation. These pass downwards into hard black slates (the so-called Genessee slates) which, in their turn, rest upon the soft gray strata of the Hamilton formation. This group of sandstone and hard shale, which appears at the surface at Kettle Point in Bosanquet, and also in Warwick, is generally concealed by the clays of the region; but from the records of numerous borings, chiefly made in search of petroleum, we have been enabled to determine its thickness in many places. Thus, in a boring at Corunna, on the St. Clair river, near Sarnia, it measures 213 feet; in two borings in Cam den, 146 and 200; in Sombra, 100; in Alvinstone, eighty feet; in Warwick, and near Wyoming station, about fifty; a little north of Bothwell, about eighty; and further south, towards the shore of Lake Erie, about sixty feet in thickness. It will be understood that this varying thickness is due to the erosion along the anticlinals, before the deposition of the clays, so that in many parts of the region only the lower portions of the black slates remain, while in other places they are entirely wanting. The hard strata just described are conformably underlaid by those of the Hamilton formation, which in some parts of New York attains a thickness of 1,000 feet, but is reduced to 200 feet in the western part of the State. It consists, in Ontario, chiefly of soft grey marls, called soapstone by the well-borers, but includes at its base a few feet of black beds, probably representing the Marcellus shale. It contains, moreover, in some parts, beds of from two to five feet of solid gray limestone, holding silicified fossils, and in one instance impregnated with petroleum; characters which, but for the nature of the organic remains, and for the associated marls, would lead to the conclusion that the underlying Corniferous limestone had been reached. The thickness of the Hamilton formation varies in different parts of the region under consideration. From the record of numerous wells in the southwestern portion it appears that the entire thickness of soft strata between the Corniferous limestone below and the black shale above, varies from 275 to 230 feet, while along the shore of Lake Erie, it is not more than 200 feet. Further north, in Bosanquet, beneath the black shale, 350 feet of gray shale were traversed in boring, without reaching the hard rock beneath; while in the adjacent township of Warwick, in a similar boring, the underlying limestone was reached 396 feet from the base of the black shales. It thus appears that the Hamilton shale (including the insignificant representative of the Marcellus shale at its base) augments in volume from 200 feet on Lake Erie to about 400 feet near to Lake Huron. The Hamilton formation, as just defined, rests directly upon the solid non-magnesian limestones of the Corniferous formation. The thickness of this formation in western New York is about ninety feet, and in southern Michigan is said to be not more than sixty, although it increases in going northward, and attains 275 feet at Mackinac. In the townships of Woodhouse and Townsend its thickness has been found to be 160 feet; but for a great portion of the region in Ontario underlaid by this formation, it is so much concealed that it is not easy to determine its thickness. If we may conclude from the boring at Clinton, it would seem to be in that locality not far from 200 feet. In the numerous borings which have been sunk through this limestone, there is met with nothing distinctive to mark the separation between it and the limestone beds which form the upper part of the Onondaga or Salina formation, and consist of dolomite, alternating with beds of a pure limestone like that of the Corniferous formation. The saliferous and gypsiferous soft magnesian marls, which form the lower part of the Onondaga formation are, however, at once recognized by the borers, and lead to important conclusions regarding this formation in Ontario. At Tilsonburg, a boring showed the existence of the Corniferous limestone directly beneath about forty feet of clay, while in another boring, about two miles to the south-west, it was overlaid by a few feet of soft shales, probably forming the basis of the Hamilton formation. The first boring at Tilsonburg, as mentioned in the report for 1866, was carried to a depth of 854 feet in the solid rock. Numerous specimens of the borings from the first 196 feet, were of pure non-magnesian limestones, but below that depth similar limestone alternated with dolomite. The marls which occur at the base of the Onondaga formation were not met with in this boring, though the water from 854 feet was said to be strongly saline. I was informed by the proprietors, Messrs. Hebbard & Avery, that the well furnished, by pumping, a brine marking from 35° to 50° of the salometer, but I was not able to get any of the water, and the well was soon after abandoned, although the presence of so strong a brine would seem to show the proximity of a saliferous stratum. In a boring at London, where the presence of the base of the Hamilton was marked by about twenty feet of gray shales, including a band of black pyroschist, overlying the Corniferous, 600 feet of hard rock were passed through before reaching soft mag nesian marls, which were penetrated to the depth of seventy-five feet. Specimens of the borings from this well, and from another near by, carried 300 feet from the top of the Corniferous, show that pure limestones are interstratified with the dolomites to a depth of 400 feet. At Tilsonburg a pure limestone was met with at 524 feet from the top. At St. Mary's, 700 feet, and at Oil Springs in Enniskillen, 595 feet of limestone and dolomite were penetrated, without encountering shales; while in another well, near the last, soft shaly strata were met with at about 600 feet from the top of the Corniferous limestone, there overlaid by the Hamilton shales. It thus appears that the united thickness of the Corniferous formation and the solid limestones and dolomites which compose the upper part of the Onondaga formation, is about 600 feet in London and Enniskillen, and farther eastward, in Tilsonburg and St. Mary's, considerably greater; exceeding by an unknown amount in these localities, 854 and 700 feet. As the few observations which we as yet possess of the thickness of the Corniferous limestone in this region, do not warrant us in assigning to it a thickness of over 200 feet, it is evident that at London and in Enniskillen the hard strata which form the upper portion of the Onondaga formation, and have at Goderich a thickness of not less than 775 feet, are greatly reduced in thickness, since the volume of the two united is only 600 feet. To the south-eastward, however, the augmented thickness of the Onondaga would appear, from the results of the borings at St. Mary's and Tilsonburg, to be maintained. The thickness of this formation is, however, known to be very variable; while at the Niagara river it is reduced to 300 feet, and is apparently destitute of salt, it augments to the eastward, in central New York, where it again. attains a volume of from 700 to 1000 feet, being equal to that observed at Goderich, and becomes once more salt-bearing. The increased thickness of the formation, in these two regions, connected with accumulations of salt at its base, would seem to point to ancient basins or geographical depressions in the surface of the underlying formation, in which were deposited these thicker portions. Most of the details here given with regard to the thickness and character of the rocks of this region are condensed from the ob servations collected in my Report for 1866, pp. 241-250. They are embodied in a paper by me entitled Notes on the Geology of South-western Ontario, and published in the American Journal of Science for November, 1868; parts of which have been reprinted, with some few changes, in the last three pages. It is a curious fact that the numerous and productive salt wells of Syracuse, New York, although occurring upon the outcrop of the Onondaga formation, do not penetrate into it, but are sunk in a deposit of stratified sand and gravel, which fills up a valley of |