ANNIVERSARY ADDRESS OF THE PRESIDENT. U 



at the moving or upheaving of the rocks. He also states that in un- 

 disturbed or horizontal strata the cleavage- and bedding-planes meet 

 at an angle from 15° to 30° ; and that the slates are bad when this 

 angle is below 20°, and good when the angle rises above 25°. These 

 deductions, however, have been merely made from observation, and 

 not from any considerations connected with physical laws ; but this 

 most interesting subject will again be referred to when considering 

 his subsequent paper on the subject of cleavage, in which the actual 

 relation between cleavage and pressure is established. 



1848. — Resuming his researches in Portugal, and examining the 

 district of Oporto, he was fortunate to discover slates containing 

 several most distinctive Silurian fossils. The great difficulty in this 

 case was, that a deposit of coal and carbonaceous shales and sand- 

 stones containing impressions of ferns, some of which closely resemble 

 true coal-plants, appeared to separate the Silurian deposit from cry- 

 stalline rocks, granite, mica schist, and gneiss ; a fact which led Mr. 

 Sharpe to inquire whether it was possible that the same species of 

 plants could have been repeated at such widely separated geological 

 periods. 



1850. — Mr. Sharpe once more entered on the subject of Portugal, 

 and in a paper of great ability completes his labours upon this 

 country. The Silurian rocks, noticed in the preceding paper, are 

 again mentioned in connexion with the anthracitiferous shales ; the 

 latter underlying the former. The Tertiary deposits, the Hippurite 

 limestone, an equivalent of our Chalk, the Subcretaceous series, the 

 Jurassic series and some sandstones of an undetermined age, are more 

 fully described than in the preceding paper, and are now illustrated 

 by numerous fossils. Of the Tertiaries, the Almada beds were, on 

 the authority of Mr. Smith of Jordan Hill, classed with the miocene. 

 In respect to the Hippurite limestone, Mr. Sharpe corrected a slight 

 error of his former paper, in which he had confounded it with another 

 limestone of an earlier date. The fossils exhibit a remarkable dif- 

 ference in comparison with those of the chalk of our own country, 

 comprising no cephalopods nor brachiopods, while of thirty-seven 

 species, twenty are entirely new, and seven are species first described 

 by D'Orbigny ; so that the fossil resemblance is singularly small. 

 The fossils of the subcretaceous rocks are considerable in number, 

 though many of them also are new ; but the abundance of the Gry- 

 ph<jea Columba in the Figueras limestone seems to render the identi- 

 fication of its position satisfactory. 



The determination of much of the Jurassic series depends rather 

 on its position under the subcretaceous than on its fossils, which 

 are very rare ; but the evidence of a few Ammonites from the lime- 

 stone near Coimbra induced Mr. Sharpe to place that limestone in 

 the Jurassic system, without, however, attempting to determine its 

 position, or that of other corresponding limestones, within the 

 system. 



Below these beds occur a series of beds of sandstones and lime- 

 stones, rich in fossils of a Jurassic or oolitic type, and underlaid by 

 a coal deposit of the oolitic age, as it contains the same species of 



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