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ROCK FORT ON THE ILLINOIS RIVER. THs is an elevated cliff on the left bank of the Illinois, consisting of parallel layers of white sandstone. It is not less than two hundred and fifty feet high, perpendicular on three sides, and washed at its base by the river. On the fourth side it is connected with the adjacent range of hills by a narrow peninsular ledge, which · can only be ascended by a precipitous, winding path.

The summit of this rock is level, and contains about three-fourths of an acre. It is covered with a soil of several feet in depth, bearing a growth of young trees. Strong and almost inaccessible by nature, this natural battlement has been still further fortified by the Indians, and many years ago was the scene of a desperate conflict between the Pottowattomies, and one band of the Illinois Indians. The latter fled to this place for refuge from the fury of their enemies. The post could not be carried by assault, and tradition says that the besiegers finally succeeded, after many repulses, by cutting off the supply of water. To procure this article the besieged let down vessels attached to ropes of bark, from a part of the precipice which overhangs the river, but their enemies succeeded in cutting off these ropes as often as they were let down. The consequence was a surrender, which was followed by a total extirpation of the band.*

On gaining the top of this rock we found says Schoolcraft, a regular entrenchment, corresponding to the edge of the precipice, and within this other excava

* Charlevoix.

tions which, from the thick growth of brush and trees, could not be satisfactorily examined. The labour of many hands was manifest, and a degree of industry which the Indians have not usually bestowed upon works of defence. We found upon this elevation broken muscle shells, fragments of antique pottery, and stones which had been subjected to the action of heat, resembling certain lavas.

From this elevated spot an extensive and diversified view of prairie scenery is presented, and the objects about our encampment appeared reduced to a diminu. tive size.

"flow fearful
And dizzy 'tis, to cast one's eye so low !
The crows and choughs, that wing the midway alr

Show scarce so gross as beetles.” The soil which results from the gradual disintegration of this rock, is nearly a pure sand. On descending · we found the prickly pear (cactus) covering a consider

able portion of this soil, where scarcely any other plant is hardy enough to vegetate.

Of the height of this cliff, the estimate which we have given is merely conjectural. The effect upon the observer is striking and imposing. But we are disposed to think the effect of loftiness produced by objects of this nature is not so much the result of the actual, as of the comparative height. We have often felt, as we have on the present occasion, an impresion of grandeur produced by a solitary precipice two or three hundred feet high, rising abruptly above a flat alluvial country or lake more striking and imposing than at other times in tra versing a region more elevated ; and where “ Alps on Alps arise.” In the latter case, the eye constantly measures one elevation by another; in the former we have no standard of this kind, and hence undoubtedly overrate. Philosophically considered, the height of prominent points of a country is estimated above the level of the nearest sea. But the effect produced on the eye or the imagination begins to be felt only from that part of a mountain where it first makes a striking angle with the plain. The annexed view of this modern Oxus, is taken from a position on the opposite side of the river, directly in front of the most precipitous face of the rock.

CIRCLE OF THE SCIENCES WITH SUITABLE

REFLECTIONS. ASTRONOMICAL SKETCHE3.--NO X.-THE MOON. The opinions of astronomers are at variance with respect to the existence of a lunar atmosphere. Philosophers often reason from analogy; and because the surface of the Moon bears a striking resemblance to the Earth, in having valleys, mountains, hills, dales, volcanoes, &c., they conclude that the Moon has an atmosphere, and consequently, rain, hail, snow, and winds. Various are the arguments advanced on each side of this question by astronomers of the greatest fame.

But if we may be allowed to judge from the appearance of the Moon when our nights are clear, we may conclude that the Moon has no atmosphere. No person ever perceived either clouds or vapours on her disk, or any thing resembling them; and these must have been seen in every age by millions of mankind, if lunar clouds, &c., existed : unless we believe that there may be an atmosphere without vapours.

Mr. Ferguson observes, “ If there were seas in the Moon, she could have no clouds, rains nor storms, as we have ; because she has no atmosphere to support the vapours which occasion them. And every body knows that when the Moon is above our horizon in the night-time, she is visible, unless the clouds of our atmosphere hide her from our view; and all parts of her appear constantly with the same clear, serene, and calm aspect. But those dark parts of the Moon, which were formerely thought to be seas, are now found to be only vast deep cavities, and places which reflect not the Sun's light so strongly as others, having many caverns and pits whose shadows fall within them, and are always dark on the sides next the Sun, which demonstrates their being hollow : and most of these pits have little knobs, like hillocks, standing within them, and casting shadows also, which cause these places to appear darker than others that have fewer or less remarkable caverns. All these appearances show that there are no seas in the Moon ; for if there were any, their surfaces would appear smooth and even, like those on the Earth.” :

Dr. Brewster observes, “ The arguments adduced by Mr. Ferguson to prove that there is no sea in the Moon are very far from being conclusive. The existence of a lunar atmosphere is completely ascertained ; and the little pits and eminences which appear in the dark parts of the Moon, which are extremely even and smooth may be regarded as rocks or islands. By observations, however, on Mare Crisium, when the line which separates the enlightened from the obscure segment of the Moon passed through the large and apparantly level spot, I have found that the shaded parts of the Moon, however smooth they may appear, are not level surfaces, and therefore, cannot be seas. If there were seas in the Moon, there would be particular times when the reflected light of the Sun would render them more bril. liant than any other part of her surface ; and the light would acquire that property called polarization, which is, however, found not to be the case.”

It would appear, therefore, from these facts, that there is no water in the Moon, neither rivers, nor lakes, nor seas; and hence we are entitled to infer that none of those atmospherical phenomena which arise from the existence of water in our own globe, will take place in the lunar world.

Every particular connected with the disk of the Moon is interesting, and in many respects, astonishing. Her mountainous scenery is awfully grand. Huge masses of rock rise perpendicularly from the plains, tower to an immense height, and reflect the rays of the Sun as from a steel mirror. These rocks appear perfectly naked, or destitute of any kind of soil and vegetation. In these stupendous and terrific rocks are discovered rents and ravines, as if split or separated asunder by some tremendous earthquake or volcano : and numberless large fragments of rocks are seen near the base of these frightful eminences, as if they had been detached by some extraordinay shock or convulsion.

The surface of the Moon is admirably calculated to reflect the light of the Sun upon the Earth. If her

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