INTRODUCTION. 31 



Emamicl Kant, one of the few philosophers who have escaped 

 the imputation of impiety, has defined with rare sagacity 

 the limits of physical explanations, in his celebrated essay 

 On the Theory and Structure of the Heavens, published at 

 Konigsberg, in 1755. 



The study of a science that promises to lead us through the 

 vast range of creation may be compared to a journey in a far 

 distant land. Before we set forth we consider, and often with 

 distrust, our own strength and that of the guide we have 

 chosen. But the apprehensions which have originated in the 

 abundance and the difficulties attached to the subjects we 

 would embrace, recede from view as we remember that with 

 the increase of observations in the present day, there has also 

 arisen a more intimate knowledge of the connection existing 

 among all phenomena. It has not unfrequently happened, 

 that the researches made at remote distances have often and 

 unexpectedly thrown light upon subjects which had long 

 resisted the attempts made to explain them, within the narrow 

 limits of our own sphere of observation. Organic forms that 

 had long remained isolated, both in the animal and vegetable 

 kingdom, have been connected by the discovery of inter- 

 mediate links or stages of transition. The geography of 

 beings endowed with life attains completeness, as we see the 

 species, genera, and entire families belonging to one hemi- 

 sphere, reflected, as it were, in analogous animal and vegetable 

 forms in the opposite hemisphere. These are, so to speak, the 

 equivalents which mutually personate and replace one another 

 in the great series of organisms. These connecting links and 

 stages of transition may be traced, alternately, in a deficiency or 

 an excess of development of certain parts, in the mode of junc- 

 tion of distinct organs, in the differences in the balance offerees, 

 or in a resemblance to intermediate forms which are not per- 

 manent, but merely characteristic of certain phases of normal 

 development. Passing from the consideration of beings en- 

 dowed with life to that of inorganic bodies, we find many 

 striking illustrations of the high state of advancement to which 

 modern geology has attained. We thus see, according to 

 the grand views of Elie de Beaumont, how chains of moun- 

 tains dividing different climates and floras and different races 

 of men, reveal to us their relative age, both by the character 

 of the sedimentary strata they have uplifted, and by the direc- 



