The park, which covers the fighting area, forms a loose crescent-shaped strip over the hills which surround the city, its points abutting on the river above and below.  The chief drives of the park parallel each other, the inner one, Confederate Avenue, following, as nearly as the hills permit, the city’s line of defense, while the other, Union Avenue, forms an outer semicircle and follows, in a similar manner, the trenches of the attacking forces.

That the battlefield is so well preserved is due in part to man and in part to Nature.  Many of the hills of Warren County, in which Vicksburg is situated, are composed of a curious soft limy clay, called marl, which, normally, has not the solidity of soft chalk.  Marse Harris Dickson, who knows more about Vicksburg—­and also about negroes, common law, floods, funny stories, geology, and rivers—­than any other man in Mississippi, tells me that this marl was deposited by the river, in the form of silt, centuries ago, and that it was later thrown up into hills by volcanic action.  He did not live in Vicksburg when this took place, but deduces his facts from the discovery of the remains of shellfish in the soil of the hills.

Whatever its geological origin, this soil has some very strange characteristics.  In composition it is neither stone nor sand, but a cross between the two—­brown and brittle.  One can easily crush it to dust in one’s hand, in which form it has about the consistency of talcum powder, and it may be added that when this brown powder is seized by the winds and whirled about, Vicksburg becomes one of the most mercilessly dusty cities on this earth.

On exposed slopes the marl washes very badly, forming great caving gullies, but, curiously enough, where it is exposed perpendicularly it does not wash, but slicks over on the outside, and stands almost as well as soft sandstone, although you can readily dig into it with your fingers.

Many of the highways leading in and out of the city pass between tall walls of this peculiar soil, through deep cuts which a visitor might naturally take for the result of careful grading by the road builders; but Marse Harris Dickson tells me that the cuts are entirely the result of erosion wrought by a hundred years of wheeled traffic.

So far as I know there is but one man who has witnessed this phenomenon without being impressed.  That man is Samuel Merwin.  Merwin went down and visited Marse Harris in Vicksburg, and saw all the sights.  He was polite about the battlefield, and the river, and the negro stories, and everything else, until Marse Harris showed him how the highways had eroded through the hills.  That did not seem to impress him at all.  Moreover, instead of being tactful, he started telling about his trip to China.  In China, he said, there were similar formations, but, as the civilization of China was much older than that of Vicksburg (fancy his having said a thing like that!) the gorges over there had eroded to a much greater extent.  He said he had seen them three hundred feet deep.