OPEEATIOJSI Of MODEBJS CAUSES. 63 



3. The vast cycles of time through which these physical 

 agents have operated, accomplish by their duration what 

 they lose in force. 



4. For these reasons, the history of the past is believed to 

 explain and illustrate the present, and should be diligently 

 studied, for the right understanding of geological phenomena. 



5. Although nature's course is generally one of repose 

 and incessant orderly action, still the volcano, the earth- 

 quake, and the flood occasionally disturb the harmonious 

 play of its hidden and silent operations ; just as the serenity 

 of the atmosphere is occasionally overcast by the storm, or 

 visited by electric phenomena. In both cases the disturbing 

 causes are destined to effect an ultimate good, and work out 

 the predetermined designs of their Omnipotent Author. 



