258 KEY TO TERRESTRIAL HISTORY 



sometimes pass into folds, by which the beds are bent 

 double upon themselves, so that their order appears to 

 be inverted. Rivers, arms of the sea, the sea itself, 

 interrupt their path, and marsh and meadow-land blot 

 out large intervals from view. 



Thus the surface of the earth presents us with only 

 fragmentary glimpses into the great succession of strata 

 which record terrestrial history. In some regions, -as in 

 the Himalaya, or the Great Canon of Colorado, chapter 

 after chapter is continuously displayed as in a mighty 

 scroll before the eye ; but even in these most favoured 

 spots there are great deficiencies, and in our own island, 

 where the succession was first painfully spelled out, letter 

 by letter, as we might say, sections are even less complete 

 and their interpretation correspondingly more difficult. 



Our very first step, if we are to discover an order of 

 succession among the strata, must be to find some means 

 by which any particular stratum may be identified, a 

 mark by which it or its equivalent may be recognised, 

 even in widely separated localities, not only within these 

 islands, but beyond their confines, over all Europe, even, 

 indeed, over the whole world. 



The recognition of such a character we owe to William 

 Smith, the second of the great pioneers in the study of 

 terrestrial history, as Steno was the first. 



The centenary of this fundamental discovery has 

 been suffered to pass without notice, without comment 

 even ; but at this period, when we are engaged in 

 recounting the successes of our science during the last 

 hundred years, it is most fitting that we should recall 

 some memory of the discoverer, and trace to its fruition 

 the growth of his idea. 



The history of William Smith's life may be briefly told. 



He was born on the 23rd of March, 1769, at Churchill, 

 in Oxfordshire. His father was a small farmer belonging 



