s_ 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."