136 . REPORT — 1861. 



The Siliuiau rocks consist of gi'ey gi'its, slates, shales, flagstones, and coarse con- 

 glomerates, the latter occurring as a ^-ide interstratilied band, and taking a peculiar 

 red coloiu- as they approach their junction with the o-\erl}ing, unconformable Old 

 Red Sandstone. Fossils were stated to have been foimd by the author and W. H, 

 Bailv, Esq., F.G.S., in these Silurian rocks, and a list of them (by the latter gentle- 

 man) was given, including two corals, sbc kinds of ti'ilobites, two sorts of grapto- 

 lites, and twenty-five shells, belonging to the orders called Brachiopoda, Conchifera, 

 Gasteropoda, and Cephalopoda. 



From the paheontological e^adence aflbrdedTsy these, the rocks which contained 

 them were supposed by fill'. Baily to belong to the lower Llandovery subdi-\ision. 



i\.fter stating the general similarity of all the rocks of Knockshigowna beneath 

 the Old lied Sandstone as one group, and their resemblance to other Lower Silurian 

 rocks in the south of Ireland, the discover}' of the characteristic Cambrian fossil, 

 Olilhavtia radiata, by J. Darby, Esq., which is believed to have been foimd ifi situ 

 in these rocks, was incidentally mentioned. And iu conclusion, the Old Red Sand- 

 stone, carboniferous shale and limestone of the localitj' were each described ; and 

 the absence of the drift, except in a few places in the ueighboiu-hood, was pointed 

 out. 



On (lie Excess of Water in the Eeyion of the Earth ahout New Zealand : 

 its Causes and Effects. By J. Yates, M.A., F.B.S., F.G.S. 



The author of this memoir endeavours first to ascertain, from the best authorities, 

 the proportion of land and water on the smfacc of the globe. He finds that the 

 estimates vary between 100 land to 256 water, which is Berghaus's last estimate, 

 and 100 land to 289 water, which is the computation of Professor Link. It is 

 remarkable that these numbers arc the squares of 10, IG, and 17, and of this cu'Cuui- 

 stance the author avails himself in his subsequent arithmetical calculations. 



Such being the propoi-tion of land to water, the next question is, where to fix 

 the centre of the water so far as it is now collected on the sm'face of the globe. 

 On the authority of Berghaus, who laboured with the concurrence and advice of 

 Iliuuboldt and Bitter, the author assmnes this centre to be 40° S. of the Equator, 

 and on a meridian which touches upon the islands of New Zealand, although his 

 conclusions would not be materially aftected, if, following Ansted and some others, 

 he were to fix the point 5° nearer to the south pole. 



For the sake of simplicity and clearness in computation, he supposes all the water 

 to be collected around its centre in aimifoiTu mass, instead of being distributed and 

 ramified into oceans, seas, baj's, and straits. Thus a small circle divides the entire 

 mass of land from the entire mass of water. This circle is delineated on the globe 

 by taking the centre of the laud and drawing a circle round it with 62° 30' as radius, 

 this radius being assumed on the supposition that it is safest to take a mean between 

 the two extreme proporrions of land and water. 



In addition to these data respecting the proportions and the centres of the land 

 and water, the author shows that the mountains in the so-called Land Hemisphere 

 greatly sm-pass in elevation those of the Water Hemisphere ; and presuming tJiat 

 the moimtains in the Water Hemisphere are the highest points of submerged con- 

 tinents, he uses the mouutaius of the Land Hemisphere as gauges for measuiing the 

 general depth of the w^ater, which he finds to be nearly two kilometres. • By a 

 subsequent investigarion he finds the generfil elevation of the continents above the 

 le^•el of the water to be about one-thu-d of this quantity. 



To explain his theor}' the author employs a diagram, which is a section of the 

 earth through the meridian of New Zealand. A diameter is drawn from the centre 

 of the ocean and is intersected by a perpendicular, which is the chord of the before- 

 mentioned arc of 125°, and which divides the collected land from the collected 

 water. By the use of this diagram, and proceeding fr-om one step of mathematical 

 reasoning to another, having like'wise assumed that the hemisphere of the solid 

 earth contiguous to the great mass of water is heavier than the other hemisphere, 

 and that the solid earth has consequently a centi-e of gi-avity lying to the south- 

 eastward of its centre of magnitude, the author computes the distance between these 

 two centres to be about 1260 metres. From this apparent fact, coupled ■with the 

 general peiinanency of the surface of the teiTaqueous globe, he infers that the inteiior 



