268 THE POPULAR SCIENCE MONTHLY. 



ural science had not attained its present importance in the minds of 

 modern nations, and even to this day it is for the most part overlooked 

 by writers of history. The numerous causes under the action of which 

 the Roman Empire was destined to crumble to pieces, and to become 

 the prey of the barbarians, have been again and again set forth with 

 much learning and skill. No doubt the ancient world had grievous in- 

 ternal ills. Slavery, pretorianism, corruption of morals, and aversion 

 to matrimony, decay of civic as also of military virtue, the enervation 

 caused by over-refinement, which had exhausted every pleasure and 

 profaned ever}' ideal, and which could not find in itself the means of 

 rising above itself such are the oft-cited causes to which the inevitable 

 downfall of the Roman domination is ascribed. 



And yet the success which almost invariably attended the efforts 

 of vigorous emperors is proof that the state of affairs was not entirely 

 hopeless. Down even to a very late period of the empire's history, the 

 course of events was tolerably amenable to control and regulation, and 

 in the face of the enemy the legions did not altogether belie their 

 hereditary valor and discipline. Even in the palmiest days of the 

 Roman state they had not always been victorious. The introduction of 

 Christianity did not move the ancient world out of the ruts so much as 

 might have been expected. Though a portion of the ancient culture 

 was then thrown overboard, it nevertheless, on the whole, remained in- 

 tact. There yet stood, under the protection of the victorious cross, 

 temples, theatres, baths, halls of justice ; the multitude of the works 

 of art baffled the fury of the destroyers, and the papyrus rolls of the 

 libraries still preserved unscathed the treasures which a thousand 

 years had collected. What was needed was to oppose to the inpouring 

 barbarian hosts from the northeast a barrier which should last until 

 the tide had begun to ebb, and these hordes had themselves come under 

 the influence of civilization : then all would have been well. 



It was the opinion of Liebig, who also contemplated the downfall 

 of the ancient culture from the point of view of the natural sciences, 

 that the case was hopeless, whatever might be done. As a result of 

 his researches on mineral manures, Liebig taught that the Roman Em- 

 pire fell like the Grecian communities at an earlier day, and like the Span- 

 ish domination later, because in the countries from which the Romans 

 derived their grain the soil had become exhausted of the mineral matters 

 requisite for growing wheat, especially of phosphoric acid and potash. 1 

 This doctrine was refuted by Conrad, who shows that the fact of the 

 soil having been exhausted is not proved. In every instance where, 

 according to Liebig, the soil was exhausted by improvident cropping, 

 other reasons may be assigned for the decreased fertility ; for instance, 

 drought resulting from the decay of irrigation-works, or from reckless 

 deforestation, and the production of marshes from the want of river- 



1 "Die Chemie in ihrer Anwcndung auf Agricultur und Phsyiologie," " Einleitung in 

 die Naturgesetze des Feldbaucs" p. 86, et seq. 



