the soil in ledges. He supposes that if strata dip 40° north-west into the ground in some prominent ledge, that the rock will continue to dip so two hundred feet below the surface, unless there be some reason to the contrary. And if for the distance of one mile, he finds four ledges of rock with equal intervals between them, and all possessing the same inclination, then with reason he infers that the concealed layers between the ledges have the same dip. But if he finds two of these ledges to dip north-west, and the other two to dip south-east towards the former, then he concludes that the strata meet under ground and form a synclinal axis or a sort of basin. Of if they dip away from each other, then he concludes they must meet in the center, much like the roof of a house, only that the top is generally rounded instead of angular, and much of the crest has been worn away. Such an axis is called an anticlinal axis. By such processes of reasoning is every observation accompanied, only the geologist does not consider it necessary to repeat them with every measurement. He takes it for granted that the reader will always supply this deficiency in his own mind, if need be.

When the geologist has travelled over a section many miles in length, it is highly probable that he will have to record several axes, either anticlinal or synclinal. And it may be that he must notice the occurrence of unstratified rocks along with the stratified. These cannot be represented as occurring in layers, but the nature of their junction with the stratified ones must be carefully noted. Again, the geologist may be at a loss to know certainly how certain formations are disposed beneath the surface, especially upon high land, where the number of ledges are very scanty. Hence he need not fill out the space allotted to him by the altitude, but simply locate in their proper places the respective dips.

It is necessary often to employ two different scales in protracting sections from notes-one for the horizontal and the other for the perpendicular distances-otherwise the hills will not be conspicuous. In the section about to be described, our vertical section is one inch for every one thousand five hundred feet of elevation, and of course for the smaller altitudes proportional parts of an inch. The horizontal section is nearly an inch for every twelve miles. Hence the outline of the surface must be distorted, but this distortion will not generally be obvious to the observer.

The section extends from Mount Desert Island to the Canada

Line, crossing the strata nearly at right angles over its whole course. It passes in order through the towns of Eden, Trenton, Ellsworth, Dedham, Holden, Brewer, Bangor, Glenburn, Kenduskeag, Corinth, Charleston, Dover, Foxcroft, Guilford, Abbot, Monson, Shirley, East Moxie, Forks plantation, No. 1 R. 5, No. 2 R. 6, Parlin Pond, Jackman, Dennis, Holden and Sandy Bay. This line is nearly one hundred and eighty miles long by the map. This route was selected in preference to any other, because it was the longest one in the State which could be travelled over with a carriage, and it passed through a fossiliferous region of great importance; and it will give a good general idea of the relative position of the most important formations in the State. In future it is desirable that a large number of sections be measured parallel to this. This should be done, since the strata commonly possess a north-easterly course, and an exploration of the geology of the State by transverse lines parallel to one another, about fifteen miles apart, will afford the quickest and cheapest mode of learning its geological structure. The preceding figures will give a bird'seye view of the position of the rocks along the route of this section. Both stratified and unstratified rocks appear upon it, and every variety of dip and axis is presented. The lower section (Fig. 44,) is a continuation of the upper, (Fig. 43,) while the numerous references will explain the names of all the rocks and the localities where the observations were made; and the description, which is to follow, will give every detail minutely. As previously intimated, an enlarged copy of this section, colored, and with specimens of all the rocks mentioned by name from the very localities, will be on exhibition at the State House during the session of the Legislature. As a matter of course the representation of the larger dimensions will be the most satisfactory.

Mount Desert Island.

Mount Desert Island is chiefly composed of granitic unstratified rocks. An occasional mass of an obscure siliceous slate appears, but nowhere upon the line of the section: and for the sake of showing the relations of a more than ordinarily interesting deposit of quartz rock, which may possibly be of the same age with the slates elsewhere upon the island, we commence the section at Bar harbor, and then proceed south-west two miles to the top of Green mountain, where the regular line of the section is intersected. We

were agreeably disappointed in discovering at Bar harbor in Eden so interesting a deposit, although its dimensions in Eden are very small. The salt-water of the ocean seems very often to preserve the primitive character of many rocks within the reach of its influence, while that part of it which is exposed only to the action of atmospheric agents is woefully weathered and obscure. This fact is well illustrated in Machiasport, where it is utterly impossible to do anything with the weathered siliceous slates upon the crest of the promontory, while within the reach of tide-water the character of the rock and the dip of the strata are distinctly preserved, as well as the drift striae. So it is in a less degree in Eden. At Bar harbor, opposite Bar island, for the distance of one and a half miles, an interesting quartz rock appears on the shores, dipping at a very moderate angle and exposed in very interesting bluffs. It appears to belong to the same formation as the Rock of Flint island, described last year. We suggested a Lower Silurian age for that upon no very reliable grounds-more of fancy than real argument, because it reminded us so much of the Potsdam sandstone in its external appearance. This rock is less flinty and more sedimentary and micaceous in its character. Ripple-marks are found upon the layers, and also the curious cylindrical stems so common at Flint island. The layers dip 12° N. 20° W., quite the reverse of what they appear upon this section. But it was necessary to represent the dip in the section as south-easterly in order to show the true relation of the strata to the underlying granite-dipping away from rather than underlying the granite. The rock upon five islands lying between Bar harbor and Gouldsborough, viz: Bar island, Long Porcupine island, Ironbound island, and two others, is probably the same, and it may extend into Gouldsborough. Bar harbor is only twenty-five miles from Flint island in a straight line, and it would not be strange if these rocks are connected together under the water. We notice that quite a large promontory in Gouldsborough has the name of Grindstone point, which causes us to conjecture that a sandstone rock exists there to give the name to the point.

Going back from the shore this quartz rock is very much acted upon by the weather, and would not be recognized commonly as the same rock, and the marks of stratification are overshadowed by the planes of cleavage, so that the former are rarely noticed. Another patch of this siliceous rock not on the line of the section,

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skirts the shore of the north part of the island between Hull's Cove and Saulsbury Cove. A dike of trap containing veins of limestone appears at Hull's Cove. Probably this rock does not extend inland further than a line connecting the two coves. The dip of the strata could not be satisfactorily determined.

The first salient point in the section is Green mountain, 1,533 feet high by our Barometer. The rock at the summit is protogine, having a talcose mineral substituted for the mica of granite. The color is red. No doubt a great portion of the so called granite of the whole island is protogine. Large plates of the protogine at the summit dip 60° N. W., while near Eagle pond they are perpendicular. A few dikes of trap are found on the mountain also. The view from Green mountain is delightful. No other peak of the same :height can be found on the Atlantic coast of the United States, from Lubec to the Rio Grande, nor from any eminence on the coast, can so fine a view be obtained. We were never charmed by any view so much as by this. The boundless ocean upon the one side contrasted with high mountains upon the other, and along the shore line numerous islands appearing like gems set in liquid pearl, form the most prominent features in the scene. White sails dotted over the water glide slowly along. We know not what view can be finer than this, where the two grandest objects in nature, high mountains and a limitless ocean occupy the horizon. The emotions awakened by this scene cannot be expressed, but the scenery remains in the memory, the never dying reminescence of a beautiful portrait placed in nature's gallery by the Master Painter. The name of Eden is truly appropriate to this beautiful place.

Following the line of the section we found quite a high mountain of granite in the north part of Eden. At Thomas and Hadley's Mill, on the north shore at the mouth of a stream, there is a band of granite. The spur of the land running out to the Toll-gate is composed of a variety of gneiss, appearing rather talcose, yet abounding in feldspar. The first dip is 35° S. 20° E., or beneath the granite rocks. At the first island on the bridge road the dip is 30° S. E. At the Toll House is a narrow slaty ledge, perhaps the first of the succeeding formation, dipping 45° S. 12° E. Upon Uncle Israel's point, a mile east of the Toll House, the rock is very distinct gneiss, dipping 37° southerly, and is intersected by four trap dikes, two of which are only one foot wide, while the third, a mass of columns, is three feet wide, and the fourth, a crystalline trap, is eighteen feet wide.