70 PARAGUAY TEA PARALLAX to the Brazilian town of Corumba, lat. 18 55', and river steamers in all seasons to the junc- tion of the Sao Lourenco. The Paraguay and the Amazon feeders Xingu and Tapajos take their rise within a few miles of one another, and the watershed is so low that wooden ca- noes ascending the Tapaj6s from Santarem are constantly carried over, and descend to Villa Maria; so that, with hut little labor, almost uninterrupted navigation by steamers could be secured through the heart of the continent, from the mouth of the Plata to that of the Amazon. Up to Asuncion the navigation is easier than on the Parana; the waters are confined within narrower limits, the depth of the channel is more uniform, and no obstruc- tion is to be apprehended. The periodical rise of the river usually averages 13 ft., and occurs in January, February, and March, and in July, August, and September, thus almost corre- sponding to the periods of the fall in the Pa- rana; hence the volume of the stream result- ing from the union of the two rivers is near- ly always the same. The banks of the Para- guay are generally sloping, and rarely exceed 25 ft. above the average height of the stream. They are clothed on both sides with a mag- nificent vegetation; forests with innumerable varieties of precious timber and ornamental woods alternating with palm groves and ex- tensive grassy plains. The portion of the riv- er comprised within the tropics abounds in ja- cares (caimans) and in excellent fish. Brazil- ian mail steamers ply monthly between Mon- tevideo and Ouyaba, a distance of 2,000 m., making the trip in from 10 to 12 days ; and there are several lines of steamers between Buenos Ayres and Asuncion. The Paraguay forms a portion of the dividing line between Brazil and Bolivia, and the entire boundary of Paraguay with Bolivia and with the Argentine Republic on the west. It was made free to ships of all nations in 1852, and has remained so to the present time (1875), except during the Paraguayan war of 1865-'70. PARAGUAY TEA, See MAT. PARAHYBA. I. A N. E. province of Brazil, bounded N. by Rio Grande do Norte, E. by the Atlantic, S. by Pernambuco, and W. by Ceara ; area, 31,500 sq. m. ; pop. in 1871 (estimated), 280,000. The coast is low, but inland the sur- face is traversed by several mountain ranges, the principal of which are the serras de Bor- borema and de Teixara. In the former rises the Rio Parahyba do Norte, which empties into the Atlantic after an E. N. E. course of 300 m. The Mamanguape, emptying 18 m. further N"., is the only other considerable river. The cli- mate inland is hot, but is considered healthful. Much of the country is fit only for pasturage, and many cattle are raised. The fertile tracts are partly covered with dense forests and partly cultivated. Cotton, sugar, and tobacco are raised to some extent. During the decade ending in 1873, the yearly average export of cotton was 196,568 Ibs. ; of sugar, 185,744 Ibs. Gums, resin, and timber are largely export- ed. In 1865 an English company was organ- ized to work the gold mines in the interior. In 1873 there were in the province 126 pri- mary and grammar schools, of which 33 were for females with an aggregate attendance of 991, and 93 for males with 2,695 pupils; and there is a lyceum in Parahyba, and colleges in Mamanguape, Area, and Pombal. II. A city, capital of the province, on the right bank of the river Parahyba do Norte, 10 m. from the sea, and 65 m. N. of Pernambuco ; pop. about 14,- 000. It is divided into an old and a new town, and has good streets and well built houses. The climate is salubrious. The port is good, but vessels of more than 350 tons seldom go up to the town. There is a large coasting trade, and the steamers of nearly all the Bra- zilian lines stop here on the trips between Rio de Janeiro and Belem. The principal exports are cotton, sugar, fish, hides, rum, tafia, coffee, and cacao. A railway to extend 60 m. inland was to be begun in 1875. PARALLAX, the apparent displacement of a heavenly body arising from a change of the observer's position. The angle subtended at the body by the line joining the two stations is the measure of the parallax. As the positions of the heavenly bodies have reference in prac- tical astronomy to the earth's centre, a correc- tion for parallax is necessary in every observa- tion, except when the body is in the zenith, where the parallax vanishes. It is greatest in the horizon, and is there termed horizontal parallax. It is manifestly equal to the angle subtended by the earth's radius as supposed to be seen from the body, as the earth's radius va- ries with the latitude, and the equatorial radius is commonly selected as the measure of paral- lax. By the mean horizontal equatorial paral- lax of the moon, for instance, is understood the angle subtended by the earth's equatorial semi-diameter at the moon's mean distance. The same is the case with the sun. And even if the word equatorial be omitted, it is to be understood that equatorial parallax is signified unless the contrary be implied. The parallax and the sine of the parallax are appreciably equal for all objects except the moon, and either is used indifferently. In the case of the moon there is a difference, and unfortunately two usages are employed. "Where the mean equa- torial horizontal lunar parallax is spoken of, the word parallax is used in its usual sense ; but what is called the lunar constant of parallax is in reality the angle which has for its circu- lar measure the sine of the true parallax. An- nual parallax is the variation of a star's place by being observed from opposite points of the earth's orbit. This is extremely minute, not- withstanding the great length of the base line, and is so difficult of determination that it long defied the endeavors of astronomers to detect it. (See ASTRONOMY.) The apparent absence of stellar parallax was considered by Tycho Brahe fatal to the Copernican doctrine of the
