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the debris of animals and plants that lived and died in its waters or along its banks, when every lake and pond deposited at its bottom in successive layers the lighter or heavier materials floating in its waters and settling gradually beneath them, the process by which stratified materials are collected and gradually harden into rock is more easily understood. But when the solid surface of the earth was only just beginning to form, it would seem that the floating matter in the sea can hardly have been in sufficient quantity to form any extensive deposits. No doubt there was some abrasion even of that first crust; but the more abundant source of the earliest stratification is to be found in the submarine volcanoes that poured their liquid streams into the first ocean. At what rate these materials would be distributed and precipitated in regular strata it is impossible to determine; but that volcanic materials were so deposited in layers is evident from the relative position of the earliest rocks.

I have already spoken of the innumerable chimneys perforating the Azoic beds, narrow outlets of Plutonic rock, protruding through the earliest strata. Not only are such funnels filled with the crystalline mass of granite that flowed through them in a liquid state, but it has often poured over their sides, mingling with the stratified beds around. In the present state of our knowledge, we can explain such appearances only by supposing that the heated materials within the earth's crust poured out frequently, meeting little resistance, that they then scattered and were precipitated in the ocean around, settling in successive strata at its bottom, that through such strata the heated masses within continued to pour again and again, forming for themselves the chimney-like outlets above mentioned.

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Such, then, was the earliest American land, a long, narrow island, almost continental in its proportions, since it stretched from the eastern borders of Canada nearly to the point where now the base of the Rocky Mountains meets the plain of the Mississippi Valley. We may still walk along its ridge and know that we tread upon the ancient granite that first divided the waters into a northern and southern ocean; and if our imaginations will

carry us so far, we may look down toward its base and fancy how the sea washed against this earliest shore of a lifeless world. This is no romance, but the bald, simple truth; for the fact that this granite band was lifted out of the waters so early in the history of the world, and has not since been submerged, has, of course, prevented any subsequent deposits from forming above it. And this is true of all the northern part of the United States. It has been lifted gradually, the beds deposited in one period being subsequently raised, and forming a shore along which those of the succeeding one collected, so that we have their whole sequence before us. In regions where all the geological deposits, Silurian, Devonian, Carboniferous, Permian, Triassic,' etc., are piled one upon another, and we can get a glimpse of their internal relations only where some rent has laid them open, or where their ragged edges, worn away by the abrading action of external influences, expose to view their successive layers, it must, of course, be more difficult to follow their connection.

For this reason the American continent offers facilities to the geologist denied to him in the so-called Old World, where the earlier deposits are comparatively hidden, and the broken character of the land, intersected by mountains in every direction, renders his investigation still more difficult. Of course, when I speak of the geological deposits as so completely unveiled to us here, I do not forget the sheet of drift which covers the continent from north to south; but the drift is only a superficial and recent addition to the soil, resting loosely above the other geological deposits, and arising from very different causes.

In this article I have intended to limit myself to a general sketch of the formation of the Laurentian Hills, with the Azoic stratified beds resting against them. In the Silurian epoch following the Azoic we have the first beach on which any life stirred ; it extended along the base of the Azoic beds, widening by its extensive deposits the narrow strip of land already upheaved.

1 Devonian... Triassic: See the geological diagram and table at page 621 of WEBSTER'S INTERNATIONAL DICTIONARY.

GRAY

1810-1888

PROFESSOR ASA GRAY, the eminent botanist, was born in Paris, Oneida County, New York, November 18, 1810, and died in 1888. He studied medicine, but his enthusiastic love of botanical investigation withheld him from the practice of his profession. In 1834 he received the appointment of botanist to the United States Exploring Expedition; but, impatient of the

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delays which hindered that enterprise, he resigned his office in 1837. About that time he was chosen Professor of Botany in the University of Michigan; before that institution was opened he accepted the Fisher Professorship of Natural History in Harvard University. His first contribution to the literature of botany was "North American Gramineæ and Cyperaceæ," of which two volumes were published in 1834-35. This brought him prominently before the scientific world. His botanical career, however, may be said to date from his reading, in December, 1834, before the New York Lyceum of Natural History, "A Notice of some New, Rare, or otherwise Interesting Plants from the Northern and Western Portions of the State of New York."

In 1838, in conjunction with John Torrey, M. D., he prepared the first part of "The Flora of North America." This work has never been completed; but in its fragmentary state it is esteemed one of the most valuable contributions ever made in America to the science of botany. The collections made by the Exploring Expedition of Commodore Wilkes, during the years 1838-42, except those obtained from the Pacific coast, were placed in the hands of Professor Gray for elaboration, and the fruits of his labors are preserved in two volumes on the "Botany of the United States Exploring Expedition."

His numerous papers in the memoirs of the learned societies, although not of a popular character, comprise a large part of his most important contributions to science. The most generally interesting one is his "Memoir on the Botany of Japan in its Relations to that of the United States," which subject was followed up in his Address as President of the American Association for the Advancement of Science, delivered at Dubuque, August, 1872. His "Structural Botany" is universally accepted as one of the best expositions of vegetable physiology and morphology ever written, while his "Manual of Botany" has long been known as a standard work. He produced several books of an elementary character, among which are “How Plants Grow," "How Plants Behave," "Lessons in Botany," "The School and Field Book of Botany," etc. Professor Gray possessed remarkable qualifications for this work, his expositions being singularly clear, and his style in all respects attractive.

HOW CERTAIN PLANTS CAPTURE INSECTS1

THIS is not a common habit of plants. Insects are fed, and allowed to depart unharmed. When captures are made, they must sometimes be purely accidental and meaningless; as in those species of Silene called Catch-fly, because small flies and other weak insects, sticking fast to a clammy exudation of the calyxes in some species, of a part of the stem in others, are unable to extricate themselves, and so perish. But in certain cases insects are caught in ways so remarkable that we can not avoid regarding them as contrivances, as genuine fly-traps.

Flower fly-traps are certainly to be found in some plants of the Orchis family. One instance is that of Cypripedium, or Lady'sSlipper, which is a contrivance for cross-fertilization. Here the insect is entrapped for the purpose of securing its services; and

1 from "How Plants Behave"

2 a discharge of moisture

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the detention is only temporary. If it did not escape from one flower to enter into another, the whole purpose of the contrivance would be defeated. Not so, however, in leaf fly-traps. These all take the insect's life, whether with intent or not, it may difficult to make out. The commonest and the most ambiguous leaf fly-traps are such as Pitchers, of which those of our Sarracenia, or Sidesaddle-flower, are most familiar. A common yellowflowered species of the Southern States has them so very long and narrow, that they are popularly named trumpets. In these pitchers, or tubes, water is generally found, sometimes caught from rain, but in other cases evidently furnished by the plant, the pitcher being so constructed that water can not rain in this water abounds with drowned insects, commonly in all stages of decay. One would suppose that insects which have crawled into the pitcher might as readily crawl out; but they do not, and closer examination shows that escaping is not as easy as entering. In most pitchers of this sort there are sharp and stiff hairs within, all pointing downward, which offer considerable obstruction to returning, but none to entering.

Why plants which are rooted in wet bogs or in moist ground need to catch water in pitchers, or to secrete it there, is a mystery, unless it is wanted to drown flies in. And what they gain from a solution of dead flies is equally hard to guess.

Into such pitchers as those of the common species rain may fall; but not readily into others, not at all into those of the Parrot-headed species of the Southern States, for the inflated lid or cover arches over the mouth of the pitcher completely. This is even more strikingly so in Darlingtonia, the curious Californian Pitcher-plant lately made known and cultivated in this the contracted entrance to the pitcher is concealed under the hood, and looks downward instead of upward; and even the small chance of any rain entering by aid of the wind is, as it were, guarded against by a curious appendage, resembling the forked tail of some fish, which hangs over the front. Any water found in this pitcher must come from the plant itself. So it also must in the combined Pitcher and Tendril of Nepenthes. These Pitcher

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