326 PHYSICAL SCIENCE 



lightning and thunder. Yet he cannot change his Stoic faith 

 that fate, that is, the necessity for the happening of all things and 

 all actions, can be set aside by no force, can be altered by no 

 portents, nor averted by any prayer or sacrifice. Though he 

 admits that vows and supplications may be useful to the wor- 

 shippers, he knows that even these also are included in the 

 decrees of fate. 



These reflections lead the philosopher to a characteristic 

 peroration on the moral lessons to be derived from the subjects 

 he has been discussing. From the dangers incident to thunder- 

 storms he passes to the enforcement of the Stoic doctrine that 

 death must be despised, and everything which leads to death will 

 then cease to have any terror. 



BOOK III 



The subjects comprised in this section of the treatise have 

 reference chiefly to the springs and rivers which appear on the 

 surface of the earth or flow underneath it. The Book begins 

 with a preface, which may have been originally designed to stand 

 at the beginning of the volume. It bears internal evidence of 

 having probably been written at the time of the author's resolve 

 to take up the discussion of physical problems, as it speaks of old 

 age pressing upon him and leaving him but a short while to cover 

 the immense field which he wished to survey. The years lost 

 among vain pursuits must be repaired by diligence in the task 

 now undertaken ; night must be added to day, and every social 

 or business care which can possibly be set aside must be aban- 

 doned. The contemplation of the work before him then leads 

 the philosopher into his moralising mood, wherein he inquires 

 what should be the principal object of human life, concluding 

 with the reflection that the best thing a man can set before him- 

 self, among the ups and downs of this world, is courage to accept 

 them calmly and to be ready to meet death boldly whenever 

 summoned. To the acquisition of such a courage a contempla- 

 tion of nature will greatly conduce. 



Seneca begins his discussion of the various forms of water by 

 grouping them into two chief classes, standing in collected sheets, 

 as in lakes, or running in channels, as rivers above ground and 

 springs underneath. After a brief enumeration of various qualities 

 of water, he inquires whence the vast volume of water comes that 

 is carried down by rivers to the sea, and how it happens that 

 neither is the earth sensible of this daily loss, nor does the ocean 



