[39] An ingenious writer has honoured this discourse with an answer full of politeness, erudition, and good sense. So learned a refutation would have made the author suspect that his reasonings were entirely overthrown, had he not used the precaution from the beginning to keep himself on the sceptical side; and having taken this advantage of the ground, he was enabled, though with much inferior forces, to preserve himself from a total defeat. That reverend gentleman will always find, where his antagonist is so entrenched, that it will be difficult to enforce him. Varro, in such a situation, could defend himself against Hannibal, Pharnaces against Cæsar. The author, however, very willingly acknowledges that his antagonist has detected many mistakes both in his authorities and reasonings; and it was owing entirely to that gentleman’s indulgence that many more errors were not remarked. In this edition advantage has been taken of his learned animadversions, and the essay has been rendered less imperfect than formerly. [40] Columella says (lib. 3, cap. 8) that in Egypt and Africa the bearing of twins was frequent and even customary; _gemini partus familiares, ac pæne solennes sunt_. If this was true, there is a physical difference both in countries and ages, for travellers make no such remarks of these countries at present; on the contrary, we are apt to suppose the northern nations more fertile. As those two countries were provinces of the Roman Empire, it is difficult, though not altogether absurd, to suppose that such a man as Columella might be mistaken with regard to them. [41] This too is a good reason why the smallpox does not depopulate countries so much as may at first sight be imagined. Where there is room for more people they will always arise, even without the assistance of naturalisation bills. It is remarked by Don Geronimo de Ustariz that the provinces of Spain which send most people to the Indies are most populous, which proceeds from their superior riches. [42] The same practice was common in Rome, but Cicero seems not to think this evidence so certain as the testimony of free citizens. (_Pro Cælio_.)