Page:Encyclopædia Britannica, Ninth Edition, v. 7.djvu/187

Rh within him led him to try his fortune as an author at Rio de Janeiro. Here he wrote for the newspaper press, ventured to appear as a dramatist, and at last in 1846 established his reputation by a volume of poems Primieros Cantos which appealed to the national feelings of his Brazilian readers, were remarkable for their autobiographic impress, and by their beauty of expression and rhythm placed their author at the head of the lyric poets of his country. In 1848 he followed up his success by Secundos Cantos e sex Tilhas de Frei Antdo, in which, as the title indicates, he puts a number of the pieces in the mouth of a simple old Dominican friar ; and in the following year, in fulfilment of the duties of his new post as professor of Brazilian history in the imperial college of Pedro II., he published an edition of Bet-redo, and added a sketch of the migrations of the Indian tribes. A third volume of poems, which appeared with the title of Ultimos Cantos in 1850, was practically the poet s farewell to Rio de Janeiro and the service of the muse, for he spent the next eight years engaged under Government patronage in obtaining a personal acquaintance with the scientific institutions of Europe, was appointad on his return to Brazil a member of an expedition for the exploration of the province of Ceara, was forced in 1862 by the state of his health to try the effects of another visit to Europe, and died in September 186-4 on board the vessel that was bearing him once again to his native shores. While in Germany he published at Leipsic a complete collection of his lyrical poems, which has since gone through several editions ; the four first cantos of an epic poem called Os Tymbiros (1857) ; and a Diccionario da lingua Tupy (1858). To the publications of the Rio de Janeiro Geographical and Historical Institute he contributed a number of papers, among which the one on Brazil and Oceania has received special notice. A complete edition of the works of Dias has made its appear ance at Rio de Janeiro. See Francisco Sutero in the Rivistan Maranhense, and Wolf, Bresil Litteraire.  DIAS,, a Portuguese navigator, the dis coverer of the Cape of Good Hope, flourished towards the close of the 15th century, the date of his birth being unknown. He seems to have interested himself at an early period in geographical research, and to have been intimate with Martin Behem. In August 1486 he was appointed by King John II. to the command of a small expedition intended to carry on the work of exploration on the coast of Africa. After touching at various points on the western shore of the continent, and taking possession of them for his royal master, he sailed onward into the unknown sea and doubled the Cape without being aware of it. He touched land at the mouth of the Great Fish River. He now found that he had rounded the continent, and in his return voyage he sighted the promontory to which he gave the name Cabo Tormentoso, or Cabo de lodos los tormientos (Cape of all the Storms). This was afterwards changed by the king for the happier title it still bears. Dias arrived in Lisbon in December 1487. He afterwards commanded a ship in the first expedition of Vasco da Gama, who sent him back to Portugal after they had reached the Cape Verd Islands. He held a similar position in the expedi tion under Cabral which discovered Brazil. On the return voyage the vessel he commanded foundered in a storm on the 29th May 1500.  DIATOMACEÆ. For the knowledge we possess of these beautiful organisms, so minute as to be undiscernible by our unaided vision, we are indebted to the assistance of the microscope. It was not till towards the close of the last century that the first known forms of this group were discovered by 0. F. Miiller. And so slow was the progress of discovery in this field of scientific research that in the course of half a century, when Agardh published his Sijstema Algarnm in 1824, only 49 species included under 8 genera had been described. Since that time, however,- the microscope has been greatly improved ; and eminent naturalists in all parts of the civilized world have been induced to engage in the study of these forms. The result is that the number of known genera and species has been greatly increased ; the species found in Great Britain and Ireland may be estimated at little less than 1000; and Rabenhorst, in the index to his Flora Europcca, enumerates about 4000 forms which have been discovered throughout the continent of Europe. At a time when little was understood of the structure of these organisms they were generally known among botanists by the appellation of Bacillariaceae ; but almost all recent authors are agreed in adopting the later and more appropriate designation of Diatomaceae. Various opinions have been entertained as to the position to be assigned to these forms. The earlier observers referred them to the vegetable kingdom. Subsequent authors, including Ehrenberg, regarded them as animals ; but in consequence of their analogy to other organisms acknowledged to be vegetable, as regards their general structure, and more especially their modes of reproduction, they are now almost universally included in the vegetable kingdom, and classified with the Monocellular .Algze. The Diatomaceaj exhibit great variety in form. While some species are circular, as Coscinodiscus per/oratus (fig. 1), others are of an oval outline, as Surirella ovalis (fig. 2).

FIG. 1. Coscinodiscus FIG. 2. Surirella perforatus. x 400. ovalis. x 400.

Some are linear, as Synedra radians (fig. 3);

FIG. 3. Synedra radians. x 200.

others more or less crescentic, as Epithemia hyndmanii (fig. 4);

FIG. 4. Epithemia hyndmanii. x 400.

others again, are cuneate, as Podosphenia lyngbyii (fig. 5);

some few have a sigmoid outline, as Pleurosigma balticun (fig. 6) ; but the prevailing forms are naviculoid, as J r avicula cuspidata (fig. 7). They vary greatly also in their modes of growth, some being free, others attached to foreign bodies by gelatinous stipes, the stipes being in some species very short, while in others they are of considerable length. In some genera the forms are simple, while in others the frustules are connected together in F - _ ribbon-like filaments, or form, as in other cases, p d spli.enia zig-zag chains. In some genera the frustules are lyngbyii. naked, while in many others they are inclosed x 400. in a more or less definite gelatinous investment, or frond, 