stratified clay and sand, overlying an older blue clay (the older drift), in which were found, by Prof. Zadoc Thompson, Sanguinolaria fusca, Mya arenaria, Saxicava rugosa, Mytilus edulis, and the bottom the bones of a Cetacean associated with S. Rugosa and a Nucula or, more probably, Leda. The Leda clay of Dr. Dawson, at Montreal, is also about 120 feet above the river, or 140 feet above the level of the sea. If the so-called "Nucula" of Lake Champlain be Leda Portlandica, the Montreal beds contain the same assemblage of fossils (except Sanguinolaria fusca).* In the Montreal beds Sir Wm. Logan also found a number of the caudal vertebræ of a Cetacean. The beds at Green's Creek, Ottawa, containing the same assemblage of shells, Mallotus villosus and remains of Seals, are 118 feet above Lake St. Peter, and 140′ to 150 feet above the sea. Marine shells (Saxicava rugosa, Mya, Mytilus edulis and Tellina Groenlandica) occur at Kingston, at the entrance to Lake Ontario. Dr. Dawson shows good reason why the above-named fossiliferous deposits on the St. Lawrence and Ottawa should be considered equivalents. In addition, I am of opinion that this conclusion may be extended to the Kingston beds, and that the beds of Lake Champlain leading down to those of the Hudson are of the same date; and if so, then I cannot doubt that the laminated clay that overlies the older boulder-drift of the Hudson Valley is a large development of the same formation, the whole having been deposited at the close of the drift. period. In that case, a long marine strait filled the valley of the Hudson, and communicated with the sea that, according to Dr. Dawson, then occupied the whole of Lower Canada south of the Laurentine Chain, and, stretching westward, covered the area of Lake Ontario, and washed the great Niagara escarpment which formed its southern coast. Probable date of the origin of Niagara Falls.-It has been shown by Mr. Hall and Sir Charles Lyell, that when the Niagara escarpment rose above the water, the Falls of Niagara began by the drainage of the upper lake-area falling into the sea over the edge of the escarpment above Queenstown and Lewistown. It is not improbable that Lake Erie extended at that period much further towards the present falls; and, agreeing in the general conclusions of these observers and of Dawson, it follows that if the sea of the Leda-clay washed the base of the escarpment, the Falls of Ni This is without doubt a Synonym for Tellina Grænlandica, a common shell at Montreal. ED. agara commenced during the deposition of that clay, or a little before the close of the drift-period.* If, with accumulated data, the rate of the past recession of the Falls be actually determinable, we shall then be in a condition approximately to show the actual number of years that have elapsed since the close of the North American drift. It may perhaps appear that the approximate period of 35,000 years, given by Sir Charles Lyell for the erosion of the gorge, is below the reality. Drift and other Late Tertiary deposits at Niagara.—I have little to add to the account of the late Tertiaries of Niagara given by Sir Charles Lyell and Professor Hall. Above the falls a terrace of drift with boulders forms the left or Canadian bank of the river. Just before reaching the Horse-shoe Fall, the terraced bank recedes; and a plateau of Niagara limestone lies between it and the edge of the gorge. A road, with a deep cutting in the drift, ascends the slope on the left between Table Rock and Clifton House, at right angles to the river. First there is a gentle slope of 35 feet, then a rapid scarped rise of 85 feet, and behind the railway a second low terrace. The first and second slopes, 120 feet high in all, consist of sandy loam (Nos. 3 and two in fig. 5), scratched stones and small boulders; and the upper terrace (No. 1) is formed of 15 feet of red clay, thinly stratified, also containing angular boulders and scratched stones Fig. 5.-Section of the Latter Tertiarg beds near Niagara Falls. • It is well known that the Niagara escarpment is of older date than the drift. Lake Erie is 329 feet above Lake Ontario; and the older boulder-drift lies indifferently on the lower plain and on the table-land. No one has yet attempted to show at what period this old coast-cliff, about 400 miles in length, was formed. The upper platform, on a grand scale, bears the same physical relation to the rocks of Lake Ontario, that Oolitic escarpment and table-land in England does to the Lias and plains of New Red Marl below. of Laurentine gneiss, and of Niagara limestones and other Silurian rocks. The top of the upper escarpment of drift forms the highest part of the whole plateau. Being 135 feet above the edge of the fall, its top is 60 feet above Lake Erie, which is only 70 feet above that edge. The edge of the great escarpment above Lewiston is said by Mr. Hall to be 70 feet above the top of the fall; and therefore the escarpment No. 1 of the accompanying diagram (fig. 5) is also 65 feet, and No. 2, 50 feet higher than the top of the escarpment above Lewiston, and 45 feet above Lake Erie. If this drift once extended across the space now occupied by the gorge, as shown by the dotted lines, Lake Erie may originally have extended thus far, and after a time the river gradually cut out a channel in the drift and formed both terraces; or else an original terraced channel existed, formed during the emergence of the country, the terraces being formed by marine denudation.* The lower terrace has, in part at least, been excavated by the river, which, before the formation of the gorge, here spread into a broad reach, like that above the Falls. It is on a continuation of this platform, about a quarter of a mile below Clifton House, between the drift-terrace and the edge of the gorge, that the strata containing existing river-shells occur (fig. 6). Fig. 6.-Section showing the position of the Freshwater beds above. the Gorge of the Niagara. 3. RIVER 4 1. Freshwater beds. This drift-terrace Sir Charles Lyell has shown to be as old as the Mastodon-period. The freshwater beds lie in a shallow hollow on the limestone. They consist of remodelled drift, and some of ⚫ It deserves to be stated, that half-way up the cutting, on the surface, I found a Cyclas; and another was found by Sir Wm. Logan, with whom I measured the section, on the same terrace, behind Clifton House. Some bits of plate of the "willow-pattern," however, lay near my shell; and that found by Sir Wm. Logan was on ground that had been stirred with the spade; and we came to the conclusion that the evidence they afforded was of very doubtful value. the stones are scratched; but whether the scratches made in the older drift-period have not been worn away, or whether the stones were scratched by river-ice is uncertain. The floor of Niagara limestone is here deeply furrowed, the striations and minor scratches crossing each other at various angles; but the majority run S. 30° W. They follow the general direction of the other striations of the country, that underlie the drift. On Goat Island, Sir. Wm. Logan and I observed that the fluviatile strata lie on drift,-a circumstance, I believe, not previously noticed. It consists, at the base, of sand; and above, of clay horizontally and evenly bedded, containing scratched stones and boulders. As shown in Sir Charles Lyell's diagram*, at the eastern end of the island the Niagara limestone rises a few feet above the river, in the still recesses of which are numerous living shell-fish. Between this and the summit of the island overlooking the Falls, there is a gradual fall of 15 feet, showing the slope of the river-bed when Goat Island was covered with water. The drift at this point is 29 feet thick, and the freshwater beds above 10 feet, giving 39 feet for the height of the island above the water at the edge of the Falls. Allowing a dip of 25 feet in a mile for the general dip of the limestone, Goat Island was covered with water when the Falls were probably about one mile and a half further down than at present. With regard to the retrocession of the fall, as might be expected, its rate is fastest when the body of falling water is greatest, this cause of waste being far more powerful than the winter's frost. Towards the base of the edges of the Horse-shoe Fall, and the American Fall, blocks of limestone are accumulated in great heaps, while in the middle of the Horseshoe Fall the turmoil is so great that it scoops out the shale beneath so deeply that the great fallen blocks are lost in the abyss. Where the body of water is small in the American Fall, the edge has only receded a few yards (where most eroded), during the time that the Canadian Fall has receded from the north corner of Goat Island to the innermost curve of the Horse-shoe Fall. * Travels in North America, vol. i. p. 20. ART. XXVI.-On Ozone. By CHARLES SMALLWOOD, M.D., LL.D., Professor of Meteorology in the University of McGill College, Montreal. [Continued from page 169.] The method now almost universally adopted for ascertaining. the presence of ozone in the atmosphere is from its action on the iodide of potassium and starch. A portion of the iodine is set free by the action of the oxygen and combines with the starch, giving rise to the fine blue colour so distinctive of the presence of ozone. The test papers are prepared by boiling one drachm of pure starch in one ounce of distilled water, and when cold, by adding ten grains of the iodide of potassium. This solution is to be carefully and evenly spread upon good glazed paper by means of a soft brush, or a sponge may be substituted. I have found that "glazed" or "sized" paper is preferable to bifulous paper. "Cream-laid letter-paper" is that used here-the solution is more evenly spread over the surface. It is then to be quickly dried, cut into pieces of about 4 inches long by 1 inch broad, and kept in a dry place, free from light and air, until required. Schonbein's ozoneometer consists of 750 slips of such paper, which is sufficient for a year. I have found that strips of fine calico, being previously well washed, and then dipped into the solution, answer equally well. I have been in the habit of using them here thus prepared, when long lengths were required, as in the apparatus where time becomes an element of the observation. These strips of paper are exposed to light, free from sun or rain, and are removed at 6 A.M. and 10 P.M., daily. These hours are adopted so as to correspond with the other instrumental observations. The date and hour is inscribed upon them, and the variable amount of ozone indicated is estimated by comparison with a scale of tints. The zero (°) of this scale, or ozoneometer as it is called, is perfectly white, increasing gradually, until a very deep blue or really black shade is obtained, which is denominated 10; the intermediate shades are easily estimated. The mean of these two daily observations forms the daily mean. The deep shades in the ozoneometer, although kept from light and air, are subject to changes by gradually becoming lighter; but a scale of artificial tints may be used, which will be permanent. Dr. Moffatt of England, who has devoted many years to observation on ozone, encloses his slips of paper in a small box without a bottom, so as to keep it shaded from light as well as rain. Observations were carried on |