1886.] ON VARIATIONS OF CLIMATE IN THE COURSE OF TIME. 



17 



alone it is impossible to form an idea of the time it has tåken 

 to form, because in the time a layer in one place upwards of 

 several 3^ards in thickness has been forming-, only an inch has 

 formed in another, whilst in a third place in the same time the 

 formation has ceased or older layers even carried away. But 

 we hp.ve a means whereby we may ascertain the time it has 

 tåken to form a layer viz., the study of the remaius of the flora 

 and fauna found in the same. The most frequent species have, 

 ceteris paribus, the most chance of being preserved. When 

 therefore, we tind that fossils, as is often the case, vary from 

 stratum to stratum, we must assume that this proves that great 

 changes took place in the fauna and the flora during the forma- 

 tion of such strata. What was stated above with regard to 

 the variations in the peat bogs of remains of plants from layer 

 to layer may be applied to variation of strata through all ages. 

 The examination of the fossils in the strata teach us respect for 

 Time. The fossils vary quickly even in strata of small thickness. 

 In one stratum we find remains of distinct animals and plants, 

 and in the one above, although perhaps only an inch atweit, 

 we tind others quite different. A thin stratum of a couple of 

 inches is sometimes distinguished by peculiar animals and plants, 

 so that the stratum may be recognized over large areas by the 

 aid of the same. When two strata of different nature alternate, 

 it is generally found that one kind of stratum contains certain 

 fossils and that those of the other are quite different. The 

 theory of periodical variations of the climate explains all this. 

 Because if the sea currents varied in stren gth, the temperature 

 of the water, and consequently the marine fauna and flora, must 

 have changed too; with a higher temperature of the sea the 

 moisture of the air and the rain-fall must have increased, and 

 thus would a periodical change of the sea-currents have the effect 

 of causing variations of the strata. It is exactly such strata of 

 vary ing nature, and varyiug forms of fauna and flora, which 

 would build the geological formations of the earth. 



We have seen how this theory explains a numher of various 

 puzsles to scientists viz., the scattered extension of species of 



Vid.-Selak. Forh. 1886. No. 8. 2 



