LECTURES ON GEOLOGY. ^45 



In order to account for the greater heat of climate during the 

 first ages of the world, geologists are now beginning generally to 

 revert to the opinions of Leibnitz and Descartes, of the cooling 

 down of the earth into its present condition from a state of igneous 

 fusion. The chief arguments in favour of this hypothesis, are, the 

 ellipsoid figure of the earth, which is the same that a fluid body 

 would assume with the same period of rotation} the volcanic 

 origin of the primary rocks ; the marks of more violent action of 

 extinct than of recent volcanoes, as exhibited in the various trap 

 and basaltic formations of the Giant's Causeway, Staffa, the Rowley 

 Hills, &C.J the tropical temperature of the Polar Regions during 

 the deposition of the coal strata, which in Spitzbergen and Melville 

 Island, are associated with the same plants as in lower latitudes ; 

 and lastly the increase of temperature both of air and water in 

 wells and mines in proportion to their depth. This degree of heat 

 varies in different places, but not in relation to the latitude 3 and 

 below the level at which it ceases to be affected by atmospheric 

 changes it increases one degree of Fahrenheit for about every 60 

 feet of depth. In the present imperfect state of our knowledge of 

 geology, we have no data for determining the absolute age of even 

 the crag, the most recent of the British strata, if we except a few 

 beds of recent shells lately discovered on the Lancashire coast j 

 and when we reflect that the aggregate average thickness of the 

 sedimentary strata is about one mile, the mind is lost in the con- 

 templation of the time necessary to form such an accumulation. 



We are also unable to answer another interesting question, viz., 

 at what period of the series man became an inhabitant of the earth j 

 but from the total absence of the remains of human beings even in 

 the diluvial stratum, it is generally concluded that but a small por- 

 tion of the earth was peopled at the time of that catastrophe. 



LECTURE II. 



The Lecturer commenced by stating that at the present and 

 following meeting of the Society, he should direct the attention of 

 his audience to the more immediate object of these lectures, viz., 

 the description of the strata that are found in the neighbourhood of 

 Birmingham, beginning with the old red sandstone or quartz rock, 

 the lowest in the series, and concluding with the new red sand- 

 stone, the latest, being that upon which the town is built. 



The old red sandstone of the district is confined to the Clent 

 Hills, and to a part of the Lickey Range ; and the quartz rock to 

 another portion, which, as it exhibits more sections than the Clent 

 Hills, and the gradual passage of one rock into the other, will form 

 a better subject for description. 



The Lickey is formed of two ranges of hills, which have been 

 named the Upper and Lower Lickey, by Dr. Buckland, who first 

 examined and described them accurately. According to him, the 

 Upper Lickey is composed of new red sandstone, but there is 

 reason to believe that this is a mistake, and that it belongs to the 

 dame formation as the Clent Hills. The Lower Lickey consists of 



