It is not on men alone that these blood-thirsty insects fasten themselves. Horses, dogs, and many wild animals are subject to their attacks. On the necks of horses they are observed to attain a very large size. It is, nevertheless, sufficiently evident that, like mosquitoes and other bloodsucking insects, by far the greater number of wood ticks must spend their lives without ever establishing themselves as parasites on any animal, and even without a single {8} opportunity of gratifying that thirst for blood which, as they can exist and perform all the common functions of their life without its agency, would seem to have been given them merely for the annoyance of all who may fall in their way. Among many other plants, common to the low and fertile parts of the United States, we observed the acalypha, and the splendid lobelia cardinalis, also the cardiospermum halicacabum, sometimes cultivated in the gardens, and said to be a native of the East Indies. It is a delicate climbing vine, conspicuous by its large inflated capsules. The acacia (robinia pseudoacacia), the honey locust, and the ohio æsculus are among the forest trees, but are confined to the low grounds. The common black haw (viburnum lentago), the persimmon or date plum, and a vitis unknown to us, occur frequently, and are all loaded with unripe fruit. The mistletoe, whose range of elevation and latitude seems to correspond very nearly with that of the miegia and the cypress, occurs here parasitic on the branches of elms. In the sandy soils of the hills, the formidable satropha stimulosa is sometimes so frequent as to render the walking difficult; it is covered with long and slender prickles, capable of inflicting a painful and lasting wound, which is said to prove ruinous to the feet of the blacks in the West Indies. The cacti and the bartonias had now disappeared, as also the yucca, the argemone, and most of the plants which had been conspicuous in the country about the mountains. The phytolacca decandria, an almost certain indication of a fertile soil, the diodia tetragonia, a monarda, and several new plants, were collected in an excursion from our encampment. The red sandrock is disclosed in the sides of the hills, but appears less frequently and contains less gypsum than above, though it still retains the same peculiar marks, distinguishing it as the depository of fossil salt; extensive beds of red argillaceous soil occur, and are almost {9} invariably accompanied by saline efflorescences or incrustations. We search in vain, both in the rocks and the soils, for the remains of animals; and it is rare in this salt formation to meet with the traces of organic substances of any kind. The rock itself, though fine and compact, disintegrates rapidly, producing a soil which contains so much alumine as to remain long suspended in water, tinging with its peculiar colour all the rivers of this region. It has been remarked, that the southern