The relation of density, in the three great divisions of London, give thirty-five, one hundred and nineteen, and one hundred and eighty square yards to each inhabitant. The densest portion of Liverpool, with its lofty and immense brick ranges of buildings, swarming with industrial life, gives more than eighty square feet to each person. The early Roman camps, which are a marvel to military men, and the closest known to military science, gave to the ordinary legion three hundred and sixty-seven square feet of area to each man. The plans of Polybius give two hundred and thirty square feet to each soldier of the consular army of two legions, numbering nearly eighteen thousand men, and the descriptions of Hyginus give similar ratios. [Illustration: _PLAN OF PRISON GROUNDS_ ANDERSONVILLE _Measured by Dr. Hamlin Copy right secured_ J. H. BUFFORD'S LITH BOSTON.] The encampments of the United States infantry afford, in the most restricted portion (between stacks of arms and kitchens), two hundred and forty-four square feet per man, or seventeen hundred and thirty-one square feet per man for the whole camp. The space allowed by law for barracks alone is fifty-four square feet for each soldier, reckoned on the basis of a full complement of men. The rules of the rebel army concerning camps are the same as those of the regulations of the United States army. The United States prison at Elmira contained six thousand men, and extended over forty acres. The other prisons, at Chicago, Johnson's Island, Point Lookout, and Fort Delaware, were provided with spacious exercise grounds, and furnished with covered barracks, built of proper form, and fitted up with the required conveniences of life. Belle Isle, which held ten thousand prisoners, had but six acres, and no shelter, no conveniences whatever. Andersonville, which contained over thirty thousand prisoners, had in the stockade, before enlargement, but eighteen acres in all, and but twelve acres for the use of the prisoners, minus the dead line and the marsh. The prison at Dartmoor, in England (which was a paradise in comparison with Andersonville), where our prisoners were held in captivity by the English during the last war, furnished two hundred to three hundred square feet to every prisoner in the barracks, besides allowing spacious yards, where the prisoners were permitted to exercise daily. There were there seven large two-story stone buildings, each one hundred and eighty feet in length. Five thousand prisoners enclosed within twenty acres of land at Dartmoor, thirty thousand in twelve acres, or thirty-five thousand in twenty-two acres, at Andersonville. VIII.