THE ROMAN WORLD 143 



coveries, nor even of imparting such knowledge as they had, 

 outside the ranks of their own gild. 



SLAVE LABOR IN ANTIQUITY. It must never be forgotten 

 that throughout antiquity, and to a great extent even until very 

 recent times, the labor question was wholly different from what 

 it is to-day. Instead of the labor-saving machinery which is so 

 extraordinary a feature of our time, but which was practically non- 

 existent before the end of the eighteenth century, the slave was the 

 machine for all heavy labor. It is not likely that he was ever a 

 particularly cheap machine, but in the mass he was powerful, and 

 it was probably largely by his labor that the fields were cultivated 

 and irrigated, and that dams and ditches, walls and towers, roads 

 and bridges and pyramids and temples, were built and fortified. 

 It is notorious that the so-called " ships " of war, the galleys, 

 were manned by slaves, even down to modern times. It is difficult 

 to determine the efficiency of labor of this kind because we are 

 generally ignorant as to the time factor, but whether from our 

 modern point of view inefficient or not, the results were often re- 

 markable and sometimes, as in the case of the Pyramids, stupendous. 



JULIUS CAESAR AND THE JULIAN CALENDAR. JullUS Caesar 



himself undertook two great problems of practical mathematical 

 science : the rectification of the highly confused calendar, and 

 a survey of the whole Roman empire. In the year 47 B.C. the 

 accumulated calendar error amounted to not less than 85 days. 

 Reform was accomplished by a decree making the year con- 

 sist of 365 days with an additional day in February once in four 

 years. The survey, of which the results were to be shown in a 

 great fresco map, was not carried out until the reign of Augustus. 

 VITRUVIUS ON ARCHITECTURE. The most famous ancient work 

 on building and kindred topics, including building materials, is 

 that entitled De Architecture, , by Vitruvius, a Roman architect 

 and engineer living (about 14 B.C.) in the age of Augustus. This 

 celebrated work was the only one of importance on architecture 

 known to the Middle Ages, and was the guide and text-book of 

 the builders of that period as well as of those of the Renaissance. 

 The book (now easily accessible in translation) is in part a 



