264 Count Gaston de Saporta on the Temperature 



kingdom, by displaying what we may learn, by the study of 

 plants alone, as to the degree of temperature of the periods to 

 which they belonged. The field, when thus limited, is still 

 immense, and can only be very imperfectly traversed ; moreover 

 I have neither the time nor the power to explore it otherwise 

 than for the purpose of placing in it a few landmarks. 



For the sake of clearness I shall divide this memoir into three 

 pai'ts : — 



In the first I shall enumerate the views of which the examina- 

 tion of fossil plants had led to the most general adoption_, until 

 lately, as to the ancient and successive states of the temperature. 

 In a second part I shall take up these same notions, to complete 

 and rectify them, as there may be occasion, by means of the most 

 recent researches. Lastly, in the third I shall establish the 

 legitimate consequences of these observations. 



I add this preliminary reflection — that, as we have to do with 

 investigations relating to temperature, the examination of the 

 vegetable kingdom is the more important because, in the present 

 state of things, plants constitute so many delicate instruments^ 

 graduated with precision, capable of marking the smallest ther- 

 mometric variations j this must likewise have been the case in 

 past times, of which the laws appear to have been in constant 

 harmony with those which prevail at the present day. 



When, during the first twenty years of this century, fossil 

 plants were first observed, and a certain regularity was found 

 to occm* in their mode of living and succeeding each other, the 

 divisions which constitute the scale of strata were still few in 

 number and imperfectly limited. A. Brongniart, who brilliantly 

 inaugurated this science in France, was the immediate disciple 

 of Cuvier ; that is to say, he was inclined to assume a certain 

 number of epochs, at the conclusion of which the organisms 

 were completely renewed, whilst within each of these epochs 

 the changes were only partial, relative, and local. However, 

 with the imperfect materials which geologists had then at their 

 disposal, it was impossible for them to determine either the 

 duration or the mode of termination of these biological periods 

 — although they were tacitly inclined to reduce towards unity 

 phenomena of various orders, and consequently to make them 

 coincide with the successive faunas established by Cuvier, each of 

 vvhich they supposed to have characterized exclusively one of the 

 intervals favourable to the development of life, called periods of 

 calm, in opposition to the violent catastrophes which must have 

 separated them. 



As regards plants alone, they could already specify a certain 



