32 THE HISTORY OF SCIENCE 



due reference to airs and waters. Vitruvius had the 

 Roman practical and regulative genius, not the ab- 

 stract and speculative genius of Athens. 



The second book begins with an account of dif- 

 ferent philosophical views concerning the origin of 

 matter, and a discussion of the earliest dwellings of 

 man. Its real theme, however, is building-material 

 brick, sand, lime, stone, concrete, marble, stucco, 

 timber, pozzolano. In reference to the last (vol- 

 canic ash combined with lime and rubble to form a 

 cement) Vitruvius writes in a way that indicates a 

 discriminating knowledge of geological formations. 

 Likewise his discussion of the influence of the Apen- 

 nines on the rainfall, and, consequently, on the tim- 

 ber of the firs on the east and west of the range, 

 shows a grasp of meteorological principles. His real 

 power to generalize is shown in connection with his 

 specialty, in his treatment of the sources of build- 

 ing-material, rather than in his consideration of the 

 origin of matter. 



Similarly the fifth book begins with a discussion 

 of the theories of Pythagoras, but its real topic is 

 public buildings fora, basilicas, theaters, baths, 

 palaestras, harbors, and quays. In the theaters bronze 

 vases of various sizes, arranged according to Pythag- 

 orean musical principles, were to be used in the 

 auditorium to reinforce the voice of the actor. (This 

 recommendation was misunderstood centuries later, 

 when Vitruvius was considered of great authority, 

 and led to the futile practice of placing earthenware 

 jars beneath the floors of church choirs.) According 

 to our author, " The voice arises from flowing breath, 

 sensible to the hearing through its percussion on 



