[Footnote 66:  The actus was the head land or as much land as a yoke of oxen could plough at a single spell without stopping, and measured 120 feet in length and four feet in width.  Cf.  Pliny, H.N.  XVIII, 3.  Hence the square of the head land became the basis of the Roman land measure.  With the derivation of the actus may be compared that of the English furlong (furrow-long) and the French arpent (literally, head land).]

[Footnote 67:  On the socialistic principle of Strepsiades in Aristophanes’ Clouds that the use of geometry is to divide the land into equal parts.]

[Footnote 68:  As it is difficult to appreciate that the Roman Campagna was formerly populous with villas, when one contemplates its green solitudes today, so when one faces the dread malaria which there breeds, one wonders how the Romans of the Republic maintained so long their hardy constitutions.  It is now agreed that there was no malaria in the Land of Saturn so long as the volcanos in the Alban hills were active, because their gases purified the air and kept down the mosquitoes, and geology tells us that Monte Pila was in eruption for two or three centuries after the foundation of Rome.  By the beginning of the second century B.C. the fever seems to have become endemic.  Plautus and Terence both mention it and Cato (CLVII) describes its symptoms unmistakably.  In his book on the effect of malaria in history, W.H.  Jones expresses the opinion that the malady was brought into Italy from Africa by Hannibal’s soldiers, but it is more probable that it was always there.  See the discussion in Lanciani’s Wanderings in the Roman Campagna.  In Varro’s time the Roman fever had begun to sap the vitality of the Roman people, and the “animalia minuta” in this passage suggests that Varro had a curious appreciation of what we call the modern science of the subject.  Columella (I, 5, 6) indeed specifically mentions mosquitoes (infestis aculeis armata animalia) as one of the risks incident to living near a swamp.]

[Footnote 69:  In the thirteenth century Ibn-al-Awam, a learned Moor, wrote at Seville his Kitab al-felahah, or Book of Agriculture, which has preserved for us not only the wisdom of the Moorish practice in agriculture and gardening which made Spain an enchanted paradise, but also the tradition of the Arabs in such matters, purporting to go back, through the Nabataeans to the Chaldaean books, which recorded the agricultural methods that obtained “by the waters of Babylon.”  Ibn-al-Awam’s book has, therefore, a double interest for us, and we are fortunate in having it available in an admirable French translation from the Arabic by J.J.  Clement-Mullet (Paris, Librairie A. Franck, 1864).  Not the least profitable chapters in this book are those devoted to the preparation of manure in composts, to be ripened in pits as Varro advises in the text.  They show a thoroughness, a care and an art in the mixing of the various animal dungs,