While the actions of a herd of buffaloes were very similar to those of a herd of cattle, yet very dissimilar to the habit of domestic cattle was their propensity to roll upon the ground. Though a bulky, ungraceful animal in appearance, the buffalo rolled himself completely over, apparently with more ease than a horse. A buffalo, by rolling over in this manner, often dusted himself in what was known as a "dry wallow." The buffaloes' licks, which afforded salt, that mineral so necessary to their health, were the foci of all their roads, the favorite spots about which the herds gyrated and between which they were continually passing. So important were these considered when white men first entered the West that every lick was carefully included in all the maps of the first geographers. Filson's map of Kentucky, for instance, made during the Revolutionary period, contains a large number of circles with dots about them which were the signs of "Salt Springs & Licks," all of them being connected, by trails, "some cleared, others not." The saline materials of these licks are derived from imprisoned sea-water which has been stored away in the strata below the action of surface waters. When these rocks lie nearer the surface than the line of drainage, the saline materials are leached away. The saline materials increase with the depth until the level is reached where we find the water saturated with the ingredients of old sea-water. The displacement of these imprisoned waters is induced by the sinking of surface water through the vertical interstices of soil and rock, and the natural tendency of the water to restore the hydrostatic balance. This action is much more likely to occur when the rocks above the drainage are limestone or shale with an underlying bed of rock composed of sandstone or other rock through which water may permeate. That such a pressure exists and that some such process is at work is shown by the waters rising ten feet or more above the surface when enclosed in a pipe. The endurance and speed of the buffalo far exceeded that possessed by domesticated cattle. With a good start a swift horse could only with difficulty overtake a herd of buffaloes. Their gait was an awkward, lumbering gallop, and the speed which they attained was much greater than it appeared to be. When running at full speed, rough ground and an occasional tumble were taken in a matter-of-fact way and seemed scarcely to retard the progress of the herd. If a ravine intersected its trail, the herd dashed down the vertical, rocky sides and on up the opposite slope, resuming its onward rush as if no obstacle had appeared.