266 Count Gaston de Saporta on the Temperature 



absent^ but only less numerous, in the localities where these 

 plants are met with, the idea of a gradual diminution of tem- 

 perature sprang from their presence the more naturally, as the 

 European genera which still showed themselves side by side 

 with the palms were principally Smilaces, pines, Thuice, and 

 laurels — that is to say, genera which, both in Europe and North 

 America, inhabit especially the southern parts of the two conti- 

 nents, from which the palms themselves are not entirely excluded. 



The most ancient Eocene times were then very little known ; 

 indeed they are scarcely known now. Certain deposits, such as 

 that of Sheppey, in the London Clay, were ascribed to peculiar 

 causes, such as the action of a current proceeding from the 

 equatorial seas. Nothing, therefore, was opposed to the assump- 

 tion that the temperature of the Tertiary epoch, at first rather 

 hotter than at present in Europe, had then become lowered in 

 such a manner as gradually to exclude the southern types from 

 this region, and to resemble that which prevails under the same 

 latitudes at the present day. 



With the chalk observers passed at once to the unknown, not 

 only in consequence of the strangeness of the forms and their 

 confused occurrence, but also of their rarity, the incompleteness 

 of their series, and the vagueness of the classifications adopted. 

 The Chalk was regarded as a sort of intermediate period, in 

 which the vegetable kingdom, in becoming renewed, had com- 

 pleted itself by the addition of the Dicotyledons, like the animal 

 kingdom by that of the Mammalia; nevertheless the observa- 

 tions were too scanty and too confused to give rise to very pre- 

 cise conclusions ; and I must say that the investigations with 

 regard to this epoch do not yet enable us to foresee any solution 

 of the difficulties which pertain to it. 



Already, however, some great facts had come to light, which 

 still serve as the basis of our present researches. Before the 

 Chalk the Dicotyledons do not make their appearance, and the 

 Monocotyledons become rare and uncertain ; the Cycadese and 

 Coniferse, on the contrary, increase, and the ferns in their turn 

 become a necessary element of the vegetation ; the forms, in 

 general, depart more and more from those of the present epoch, 

 even under the tropics, and it is amongst the most restricted of 

 existing groups that we have to seek for similitudes; these 

 points themselves are at last wanting, and towards the base of 

 the Jurassic series the vegetation no longer presents anything 

 but analogies, becoming more and more distant, with those of 

 the actual world. 



At the date that I have selected (that is to say, about 1840) 

 the flora of the Secondary formations and those of the Trias and 

 Carboniferous formations were already well known; notwith- 



