on the Surface of the Earth. 103 



ibsbil remains must form a notion, more or less precise, respecting 

 their succession, and the opinions they have formed on this point 

 necessarily react on their tendencies, their systems, and the manner 

 in which they look for facts, and also group and explain them. A 

 palseontoiogist who should confine himself to collecting facts without 

 previously having formed some theoretical view, and who sought not, 

 under its influence, to direct his observations to the elucidation of 

 some obscure points in the history of the globe, would resemble a 

 navigator who embarks without rudder or compass, and discovers 

 new regions without having the means of determining their relations 

 to the rest of the world. Facts which, as I have already said, are 

 the useful part of the science, require some bond of connection in 

 order to excite interest, and to render them worthy of becoming the 

 objects of the philosopher's meditations. Although this bond of con- 

 nection can scarcely ever be known with certainty, every one endea- 

 vours to aim at it, and seek for its discovery ; and this he makes his 

 principal, though remote, object. The time, therefore, is not lost 

 which is devoted to the elucidation of this inquiry, and to the discus- 

 sion of the probability of the laws and theories which facts alone, it 

 is true, can convert into certainty, but which have an important in- 

 fluence on the manner of collecting, commenting upon, and general- 

 ising facts. 



I shall first consider what relates to the law of the sjpecialty of 

 fossils, a law which, as every one is aware, consists in the admission 

 that each geological epoch has had its peculiar species, and that no 

 species is found, at the same time, in the formations of two different 

 eras. This law has been keenly defended and attacked, and the im- 

 portance of its geological applications sufficiently explains the inte- 

 rest which attaches to it. 



In the first place, even the right of its bearing the title of a law 

 has been disputed by a skilful anatomist, M. do Blainville, whose 

 high authority, in subjects of natural philosophy, I most readily ad- 

 mit. I believe with him that the word Imo ought to imply the idea 

 of a more immutable and necessary principle than belongs to the 

 generalisations which the human mind draws from the study of 

 the phenomena of nature : but in applying this name to the prin- 

 ciple in question, palaeontologists have done nothing more than fol- 

 low the example which has been long set to them by natural philo- 

 sophers, physiologists, &c. In all sciences, the general expression 

 under which we assemble the conditions common to many facts, or 

 the relations which observation seems to indicate between them, has 

 been called a law ; and if it be wrong to assimilate, in some measure, 

 by this word, these incomplete and imperfect relations to the im- 

 mutable laws of nature, the same blame may perhaps be attached to 

 almost every thing that bears the name of law, either in the physi- 

 cal or natural sciences. The laws acknowledged by natural philo- 

 sophers respecting the distribution of heat or the density of gases, 



