RHENISH PRUSSIA. This portion of the Prussian dominions, situated near the Rhine, is very important for its produce and manufactures. The natural productions are equally numerous and valuable Some parts of the mountains are crowned with forests, and the declivities are covered with vineyards where the exposure is favourable. The mineral kingdom yields silver, iron, copper, lead, calamine, marble, slate, freestone, millstones, basalt, porphyry, alum, manganese, sulphur, coal, and salt. In the level parts of the north there are productive corn fields and rich pas tures ; between the mountains there are fertile valleys, where flax, hemp, hops, and tobacco are grown, and fruit and garden produce of every kind are cultivated in great abundance. Game is plentiful, and all the domestic ani mals are bred in sufficient numbers. The Rhine passes through this province for 180 miles, and is navigated by steamers. The small rivers and streams are applied to turn mills and to work manufacturing machinery of every kind. The trade of the province is very extensive. The province had, at the end of 1846, 41 cotton factories with 109,547 spindles. When we state that the province contains the important towns of Cologne, Coblentz, Elberfeld,Diisscldorf, Aix-la-Chapelle and Treves, it will he seen how rich a portion it must constitute of the Prussian dominions, in manufactures and commerce.
RHEO'METER,is an instrument by which the force of an electric or magnetic current may be measured. The word was first pro posed by M. Peclet as a synonym for galva nometer; and it has since been employed by Professor Wheatstone in a general sense, to gether with Rheoscope, denoting an instru ment by which the existence of an electric, &c. current may be ascertained ; and Rhea motor, expressing any apparatus, as an elec trical or galvanic battery, by which a current of that kind is orignated. The Rheometer or Galvanometer employed by Mr. Wheatstone is a glass cylinder resting on a stand, and con taining within it a magnetised needle, which is suspended from the cover. A graduated circle serves to show the deviations of the needle from the zero of the graduations, and the amount of deviation is read by means of a microscrope. For forces or resistances which are considerable, there are placed below the circle numerous coils of fine wire ; but for small forces a thick plate of wire making but one coil is used.