CONTENTS 



i 



PAGE 

 ON A PIECE OF CHALK [1868] 1 



(A Lecture delivered to the working men ot 

 Norwich during the meeting of the British 

 Association. ) 



II 



THE PROBLEMS OF THE DEEP SEA [1873] 37 



III 



ON SOME OF THE RESULTS OF THE EXPEDITION OF H.M.S. 



&quot;CHALLENGER&quot; [1875] 69 



IV 



YEAST [1871] 110 



