CONTENTS. 



PAGE 



ON THE STUDY OF ZOOLOGY. (A Lecture delivered at the South 

 Kensington Museum, in 1861, and subsequently published by the 

 Department of Science and Art) 81 



VII. 



ON THE PHYSICAL BASIS OF LIFE. (A Lay Sermon, delivered in 

 Eclinbugh, on Sunday, the 8th of November, 1868, at the request 

 of the late Rev. James Cranbrook ; subsequently published in the 

 Fortnightly Review} 104 



VIII. 



THE SCIENTIFIC ASPECTS OF POSITIVISM. (A Reply to Mr. Congreve s 

 Attack upon the Preceding Paper. Published in the Fortnightly 

 Review, 1869) 128 



IX. 



ON A PIECE OF CHALK. (A Lecture delivered to the &quot;Working Men of 

 Norwich, during the Meeting of the British Association, in 1868. 

 Subsequently published in MacmUlan i Magazine) 151 



X. 



GEOLOGICAL CONTEMPORANEITY AND PERSISTENT TYPES OF LIFE. (The 



Anniversary Address to the Geological Society for 1862) .... 176 



XI. 



GEOLOGICAL REFORM. (The Anniversary Address to 1he Geological 



Society for 1869) 198 



XII 

 THE ORIGIN OF SPECIES. (The Westminster Review, April, 1860) . . 222 



