60 COSMOS. 



based only on a rational foundation — that is to say, of being 

 deduced from ideas alone. 



It seems to me that a like degree of empiricism attaches to 

 the Description of the Universe and to Civil History ; hut in 

 reflecting upon physical phenomena and events, and tracing 

 their causes by the process of reason, we become more and 

 more convinced of the truth of the ancient doctrine, that the 

 forces inherent in matter, and those which govern the moral 

 world, exercise their action under the control of primordial 

 necessity, and in accordance with movements occurring period- 

 ically after longer or shorter intervals. 



It is this necessity, this occult but permanent connection, 

 this periodical recurrence in the progressive development of 

 forms, phenomena, and events, which constitute nature, obe- 

 dient to the first impulse imparted to it. Physics, as the term 

 signifies, is limited to the explanation of the phenomena of the 

 material world by the properties of matter. The ultimate 

 object of the experimental sciences is, therefore, to discover 

 laws, and to trace their progressive generalization. All that 

 exceeds this goes beyond the province of the physical descrip- 

 tion of the universe, and appertains to a range of higher spec- 

 ulative views. 



Emanuel Kant, one of the few philosophers who have es- 

 caped the imputation of impiety, has defined with rare sagac- 

 ity 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 re- 

 sisted 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 intermediate 

 links or stages of transition. The geography of beings endow- 



