Mevieirs — Professor Gregory— Blaldng of the Earth. 563 



The anticline has been much broken by faulting, and the limestone is 

 now in twelve separate parts. Careful observations of the dips prove 

 faulting to be a satisfactory explanation of this separation. The 

 Silurians are separated from the Old Red Sandstone to the west, from 

 Littlemill to Trostra, by a fault, but from Trostra to Llandegveth and 

 Graigwitli the basement bed of the Old Red Sandstone, a yellow 

 quartzose sandstone, rests with apparent conformity on the Ludlow Beds. 

 The eastern anticline is thinner than the western one. Its lowest bed 

 seen is the Wenlock Limestone of Cwm Dowlais, this being covered by 

 Ludlow Beds, which run south through Llangibby Park. A fault line 

 separates these Ludlows from the Old Red Sandstone to the east. The 

 Wenlock Shale is a brown sandy shale where its lowest beds are seen 

 in the railway cuttings near Bryn, and it becomes more sandy in its 

 higher parts, a definite sandstone occurring close to its summit. The 

 Wenlock Limestone has about 12 feet of massive limestone at its base, 

 largely formed of crinoid fragments, and, above this, irregularly bedded 

 limestone separated by thin shaly partings. Corals are scarce, Brachio- 

 pods and Trilobites common. The Ludlow Beds are, for the most part, 

 brown sandy shales, with calcareous nodules or thin calcareous layers, 

 but towards their summit they pass up into sandstones. The northern 

 half of the Inlier is far less simple than the southern in its structure, 

 and is more concealed by drift. Its western boundary is everywhere 

 obscured, but Ludlow Beds are seen here and there dipping towards 

 the Old Red Sandstone not far off the boundary. The central part 

 is composed of Wenlock Shale, and the eastern margin is composed of 

 Ludlow Beds dipping eastwards and faulted against the Old Red Sand- 

 stone. The Wenlock Limestone is not met with in this northern half of 

 the Inlier. The simplest explanation of these facts is that the Wenlock 

 Shale is (faulted aigainst the Ludlow Beds (On both sides. As the Aymestry 

 Limestone is absent from the district, it seems impossible to separate the 

 Ludlow Beds into an upper and lower division, but fossils have been 

 carefully collected in order to see if any horizons can be fixed. The 

 main boundary faults are crossed at several spots by minor east and 

 west faults, which cause small lateral displacements. 



ZRE-VIE-WS. 



I. — The Making ok the Eakth. Ey Professor J. W. Gkkgoey, 

 F.E.S., D.Sc. Ifimo; pp. yiii, 266, with 37 text-illustrations. 

 London : Williams & Norgate (Home University Library Series), 

 1912. Price Is. net. 



A HIGH standard has already heen attained by the Home University 

 Series, and the little volume now before us will command a place 

 among the best. In the small space at his disposal Professor Gregory 

 tells us the story of our earth from the nebula to the appearance of 

 life, and tells it in a style that has a distinct charm, and within his 

 pages we find accounts of the most important and up-to-date theories 

 concerning our earth. The discussion of the nature of nebulae leads on 

 quite clearly to the stating of the planetismal hypothesis, with which, 

 further, the evidence of ancient climate is shown to be in agreement. 

 In a clear way, too. Professor (jlregory traces the formation of the 

 earth's surface, and in a short chapter shows what earthquakes tell us 

 of the interior of the earth. The geographical distribution of extinct 

 animals and plants is dealt with in an interesting manner in connexion 

 with the inconstancv of oceans and continents, and the discussion of 



% 



