146 JOHN EVANS — ON TEETIAKT MAN. 



divisions in nature. In the same manner these geological divisions 

 and subdivisions, though extremely convenient, are no doubt to a 

 certain extent arbitrary. 



I need not enter into all the details of the three main divisions, 

 hut may just state that the Primary beds, which include the Coal- 

 measures and all rocks up to the Permian, are, when containing 

 organic remains at all, characterized by a certain kind of vegetation, 

 such as pines, fenis, gigantic club-mosses, and, so far as animal life 

 is concerned, by molluscs and fishes, and a few reptiles. These, 

 however, are found only in the upper part, and no such thing as a 

 mammal is known. The Secondary beds comprise rocks from the 

 Trias to the top of the Chalk, and there we find in the vegetable 

 world a considerable number of conifers, cycads, etc., deciduous 

 trees making their appearance at the close. So far as vertebrate 

 animals are concerned, reptiles of a large size are abundant, and 

 there are some few birds with teeth in their bills ; but the only four- 

 footed animals are small marsupials, or pouched animals ; no 

 mammals of a higher form being then known. When, however, we 

 come to the upper beds — the Tertiary — which comprise all the rocks 

 up to the Norwich Crag, we find that the vegetable world exhibits 

 other forms, such as angiosperms, or those which have their seeds 

 inclosed in a pod or pericarp like peas ; and the reptiles have to a 

 great extent given place to large land animals — placental mammals 

 — and the birds are true birds. These, then, are the three main 

 geological divisions ; but in addition to them there is still another 

 period more nearly approaching the present time. This is the 

 Quaternary, or, according to Sir Charles Lyell, the Post-Tertiary, 

 which he divided into the Post-Pliocene and Recent. This fourth 

 period has been also divided into the Pleistocene, the Pre-historic, 

 and the Historic. In respect to these divisions, I may mention an 

 admirable book treating of the whole subject of the antiquity of 

 man, and entering largely into details, lately written by Professor 

 W. Boyd Dawkins, called ' Early Man in Britain and his Place 

 in the Tertiary Period,' from which I have to some extent bor- 

 rowed. This evening, however, we have not so much to do 

 with this particular branch of the subject as with actual 

 Tertiary times, and these are usually subdivided into three 

 divisions — an arrangement for which we are indebted to Sir 

 Charles Lyell, who noticed that in the early deposits there was 

 only a certain small per-centage of living forms present, while in the 

 later the proportions increased. He therefore divided the Tertiary 

 Period into the Eocene, the dawn of recent species ; tbe Miocene, 

 that with a small number of recent species ; and the Pliocene period, 

 or that with more. These have been further sub-divided into the 

 Lower, Upper, and Middle Eocene ; the Lower and Upper Miocene ; 

 and the Older and Newer Pliocene. The succession of all these sub- 

 divisions, the one to the other, is perfectly established, but the 

 chronology of all is extremely difficult. There are no means of 

 judging what length of time these periods embrace ; nor are there 

 means of ascertaining how long the world remained in any of these 



