scales, notably in Acanthophis. The use of such a tail probably consists in attracting or fixing the attention of small animals, by slightly raising and vibrating the tip. The rattle no doubt acts as a warning, every snake preferring being left alone to being forced to bite. Many a man has been warned in time by the shrill sound, and this principle applies undoubtedly to other mammals. Moreover, rattlesnakes are rather sluggish, and comparatively not vicious. First they try to slink away; when overtaken or cornered they use every means of frightening the foe by swelling up, puffing, rattling and threatening attitudes; it is as a rule not until they are touched, or provoked by a rapid movement, that they retaliate, but then they strike with fury. They are viviparous, and as destroyers of rats, mice and other small rodents they are useful. The surest way of clearing a ground of them and any other snakes is to drive in pigs, which are sure to find and to eat them, without harm to themselves. They inhabit localities to which the sun has free access, prairies, rough stony ground, &c. Specimens of 5 ft. in length are not rare. Formerly common in the eastern parts of the United States, and still so in thinly inhabited districts, rattlesnakes, like the vipers of Europe, have gradually succumbed to the persecution of man.
Fig. 2.—Rattlesnake (Crotalus adamanteus s. durissus).
Rattlesnakes are confined to the New World. North-American authors distinguish a great number of different kinds, S. W. Carman (“Reptiles and Batrachians of North America,” Harvard Mus. Zool. Mem., 1883, 410) enumerating twelve species and thirteen additional varieties. E. D. Cope has split them into twenty; but all these species or varieties fall into two groups. One, Sistrurus, has the upper side of the head covered with the ordinary nine shields; only three species, of comparatively small size, in North America (Sistrurus miliarius from Florida to Sonora; S. catenatus in many of the middle states of the Union, and elsewhere, as far north as Michigan; S. ravus in Mexico).
The second group forms the genus Crotalus, in which the shields between and behind the eyes are broken up and replaced by small scales. This genus ranges throughout the United States through Central and South America into Patagonia, but is not represented on any of the West Indian islands. C. horridus, with the tail uniformly black, from Maine to Kansas and Louisiana to Florida. C. adamanteus, tail light, with black crossbands, body with a handsome pattern of rhombs with lighter centres and yellowish edges; chiefly south-eastern states, to Arizona and Mexico; the largest of rattlers, giants of 8 ft. in length having been recorded. C. confluentus, tail with brown or indistinct bands; with a continuous series of large brown or reddish rhomboidal spots on the back; Texas to California. C. cerastes, with a pair of horns above the eyes; the “sidewinder” of Arizona and California to Nevada. C. terrificus, easily distinguished by the possession of three pairs of symmetrical shields on the top of the muzzle, ranging from Arizona into Argentina. It is the only kind of rattlesnake in Central and South America. C. triseriatus, a small species, with a feebly developed rattle, on Mexican mountains, on the pic of Orizaba up to 12,500 ft.
RAU, KARL HEINRICH (1792-1870), German political economist, was born at Erlangen on the 29th of November 1792. He studied from 1808 to 1812 at the university there, where he afterwards remained as a Privatdozent. In 1814 he obtained the prize offered by the academy of Göttingen for the best treatment of the question how the disadvantages arising from the abolition of trade gilds might be removed. His memoir, greatly enlarged, was published in 1816 under the title Über das Zunftwesen und die Folgen seiner Aufhebung. In the same year appeared his Primae lincae historiae politices. In 1818 he became professor at Erlangen. In 1822 he was called to the chair of political economy at Heidelberg where the rest of his life was spent, in the main, in teaching and research. He took some part, however, in public affairs: in 1837 he was nominated a member of the first chamber of the duchy of Baden, and in 1851 he was one of the commissioners sent to England on the part of the Zollverein to study the Industrial Exhibition. A result of this mission was his account of the agricultural implements exhibited at London (Die landwirthschaftlichen Geräthe der Londoner Ausstellung, 1853). He was elected a corresponding member of the French Institute in 1856. He died at Heidelberg on the 18th of March 1870.
His principal work is the Lehrbuch der politischen Ökonomie (1826-37), an encyclopaedia of the economic knowledge of his time, written with a special view to the guidance of practical men. The three volumes are respectively occupied with (1) political economy, properly so called, or the theory of wealth, (2) administrative science (Volkswirthschaftspolitik) and (3) finance. The two last he recognizes as admitting of variations in accordance with the special circumstances of different countries, whilst the first is more akin to the exact sciences, and is in many respects capable of being treated, or at least illustrated, mathematically. This threefold division marks his close relation to the older German cameralistic writers, with whose works he was familiarly acquainted. It is a consequence in part of his conformity to their method and his attention to administrative applications that his treatise was found peculiarly adapted for the use of the official class, and long maintained its position as their special text-book. He was the economic teacher, says Roscher, of the well-governed middle states of Germany from 1815 to 1848. The book has passed through many editions; in that of 1870 by Adolf Wagner it was transformed into a new book.
In the earlier part of his scientific life Rau tended strongly towards the relative point of view and an historical method in economics, but he never actually joined the historical school. To the end he occupied a somewhat indeterminate position with respect to that school; on the whole, however, he more and more subordinated historical investigation to immediate practical interests, and in his economic politics moved in the direction of limiting rather than extending the sphere of state action. His general merits are thoroughness of treatment, accuracy of statement, and balance of judgment; he shows much industry in the