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and in many other parts of the world contain auriferous deposits.
The remaining division of the formations near Washington consists of drift alluvial or superficial deposits, and exhibits vast beds of gravel, boulders, sand, clay, &c. These may also be subdivided into two kinds, that which is uppermost containing transported masses enclosing Silurian or Devonian fossils, some fragments of petrified wood, and not being highly colored by the presence of ferruginous matters. The lower beds are deeply stained with iron, and show in places thick beds of a ferruginous conglomerate.
The flora of this District may be regarded as an inter. mingling of northern and southern forms, and exhibits but little worthy of remark which may not be likewise found along the coast region from New Jersey down to the lati tude of the mouth of the Chesapeake. The great orders of Ranunculaceae, Cruciferæ, Leguminosa, Rosacec, Umbelliferæ, Compositæ, Labiata, Orchidea, and Graminece very generally resemble in species what are found over a large circle of country around. As a notice of the genera and species individually would be out of place in this sketch, it is regarded as sufficient to indicate some of the special localities where the rarer kinds of plants may be found growing.
Among the richer spots which reward the researches of the botanist, the margins of Rock Creek and its tributaries, extending several miles in a northern direction, have been diligently visited. In the proper season, on the margin of these streams, will be found among the commoner plants two splendid lilies, two phloxes, Pulmonaria Obolaria, Apios tuberosa, spice wood, all the dwarf sunflowers,
Equisetum and ferns, whilst towering above all stands the great purple Eupatorium. One of the peculiarities of this locality is found in the marshy heads from which streamlets issue and flow into the creek or its branches. These frequently cover several acres, and are generally shaded by large trees, interspersed among which are the magnolia, poison sumach, Chionanthus, or fringe-tree, and the Nyssa or gum. These tracts are very boggy, and covered with Sphagnum (a moss), out of which, sometimes as early as the 15th of January, the skunk cabbage (Symplocarpus) in vast numbers throws up its rich-colored spathe and flower, where also may be observed the curious young shoots of the Osmunda, or flowering fern, which are abundant. The most beautiful of our orchids are also to be seen later in the season in these dirty and inaccessible places, such as Arethusa, Pogonia, Triphora, Platanthera, and Calopogon. A search among the clumps of wild roses and alders will be repaid by a few plants of Kalmia glauca, Drosera, or sun-dew, and the rarer Lycopodiums. Among the hills bordering on these streams there is a locality which furnishes Dodecatheon meadia, Batschia canescens, and Gualtheria procumbens, which are exceedingly rare.
The stretch of country known as the slashes,” within the city limits, was long the profitable resort of botanists, but is now nearly obliterated. The soil consists of a stiff clay, which, for the most part, is spongy, from holding water nearly all the Fall, Winter, and Spring. In Summer it is hard-baked and dry, except in spots occupied by small, stagnant pools. These conditions once furnished protection for many curious plants which flowered before the dry season commenced. Among these, now no longer
seen, and much lamented, was an Utricularia, and many of the orchids. Drainage, grubbing, and perpetual depasturation has reduced the slashes to mere surfaces for the production of malaria, and as proper cemeteries for the dead animals of the city. Enough, however, remains to show that they were formerly covered with thickets of bramble, sweet gum, maple, magnolia, winterberry, wild roses, and white azaleas. Around the clumps and roots of these are still seen growing Arethusa, Pogonia, Habenaria, several Violas, with Arnica, Asclepias, and Callitriche, in the more open spaces.
In the immediate vicinity, the flat districts on the Virginia side of the river, which are frequently overflowed by the tides, furnish the usual array of aquatic species. These are Pontederia Calla, Orontium, Sagittaria, &c., among the herbaceous plants, intermixed with a shrubby growth of grapevines, alnus, willow, button bush, or Cephalanthus, with Typha, or cat-tail, and Zizania, or wild rice, to represent the grasses. Not far distant from these, on not much drier soil, may be seen the red and blue Lobeliu, Chelone, Bidens, or marsh marygold, a little passion-flower, and the favorite blue Erpatorium or Conochinium. Floating in the waters of Four-Mile Run may be detected the graceful Nymphea odorata, and it is reported that the great yellow Nelumbium, or water chinquapin, may be gathered at Acquia Creek. Black birch, the silky cornel, sycamore, and hackberry, line the margins of the swamps, and are overrun by climbers, such as trumpet-flower, ampelopsis, poison oak, Celastrus, and Mikania. These overshadow half stagnant pools filled with Myriophyllum, Chara, Ceratophyllum, and Anacharis, which abound with infusorial and other microscopic forms. In
the river flats there is little else than the Valisneria, the food of the canvas-back duck.
Among the forest trees may be found about fifteen species of oaks, mostly of the commoner sorts. Those which deserve notice as being scarce are the scrub or bear oak, the laurel oak, and Bartram's oak, or Q. heterophylla ; the latter, upon the authority of two observers, being found within a few miles on a northeast line from the city. The chesnut, hickories, black walnut, and butternut, are common. The dwarf pine, Pinus inops, associated with Virginia cedar and sassafras, clothe the barren old fields, giving them an uninviting appearance. But few forest trees of original growth are now seen near the city. In private grounds or parks, on Boundary Street, in Washington, or on Georgetown Heights, may be observed some fine examples of oaks, which are preserved with commendable care. A few groves of the yellow pine are still standing among the hills, a few miles north of the city, whilst near the river margin may be seen some large specimens of American elm and linden.
On the rocky bluffs on the south side of the river, and above the Aqueduct, we have, in the early Spring, rich masses of color from the red flowers of the Judas tree, the white flowering Amelanchier and dogwood, in contrast with the dark foliage of the surrounding pines and cedars; and, at the water level of the same localities, the witch hazel, or Hammamelis, produces its yellow flowers in the Fall and its fruit in the Spring. Farther up the river, and near the Little Falls Bridge, a single settlement of Rhododendron maximum has been found half buried in the kalmia thickets overhanging the river. .
Here we encounter the evidences of the only strange
flora which can be said to intrude into our District, most of the species of which can be traced up to the far western sources of the Potomac. They have been observed all over both sides of the river, as high up as the Great Falls, and many
of them may be collected at or near High or Rock Island, about a mile above Little Falls Bridge. It will suffice to enumerate a few of the more common, viz.: Opuntia Muscari, Phlox divaricata, Phacelia, two species of Sedum, Dracocephalum, the blue Baptisia, Jeffersonia, Trillium, Asarum, a rare orchid, Tipularia discolor, Erigenia bulbosa, Pentstemon, &c. They are also accompanied by the papaw, Dirca palustris, or leatherwood, Schollera and Lythrum.
Among the ferns we find about twenty species, which are abundant and well grown. The only species that need be mentioned for their scarcity is the Camptosurus, or walking fern, at Cabin John Aqueduct Bridge, and Asplenium augustifolium, at High Island, before referred to.
The temperature of Washington in the shade) ranges from 105 degrees above to twelve degrees below zero, of Fahrenheit's scale. The mean of January, the coldest month, is about 32°; and of July, the warmest month, about 77o. The mean temperature of the year is about 56o. Sudden changes of temperature are sometimes experienced, the thermometer falling 20 or 30 degrees in a few hours. These changes are not local, but may be traced, in different degrees, over a large extent of country, and come with a west or northwest wind. The river is generally closed in the early part of January, and, in very cold