condition, and plants in prodigious abundance. Accidental cases of color or structure externally resembling these may be found under similar conditions—more or less complicated figures in which it will be often easy to find such resemblances as clouds or 
Fig. 1.—Stone, the fracture of which presents the appearance of a feathered fowl. (After Mylius.) the arabesques of a tapestry give us. Fig. 1 represents an example of this kind, from the Saxonia Subterranea of Mylius (Leipsic, 1709); it is the picture of a stone the fracture of which exhibits spots making out the figure of a fowl with her plumage, comb, and the scutels of the tarsi. A class of accidents Of a different Character is especially fruitful of surprises of the kind under consideration. These are the dendrites, which are very frequent in joints of rocks of all ages, and of which Fig. 2 gives a very exact idea. At Romainville and
Fig. 2.—Dendrite, composed of small crystals of ferriferous oxide of manganese—the acerdesis of mineralogists; found in the Assures of a lithographic limestone. (Specimen from the Museum of Natural History; half the natural size.
Argenteuil, near Paris, we may see in the plaster quarries that all the fissures crossing the beds of marl, whatever their color, white,
