11. In what follows we shall suppose the chart drawn on a plane-surface; and our descriptions shall consist of what we ourselves have observed in our travels by land and sea, and of what we conceive to be credible in the statements and writings of others. For ourselves, in a westerly direction we have travelled from Armenia to that part of Tyrrhenia[730] which is over against Sardinia; and southward, from the Euxine to the frontiers of Ethiopia.[731] Of all the writers on Geography, not one can be mentioned who has travelled over a wider extent of the countries described than we have. Some may have gone farther to the west, but then they have never been so far east as we have; again, others may have been farther east, but not so far west; and the same with respect to north and south. However, in the main, both we and they have availed ourselves of the reports of others, from which to describe the form, the size, and the other peculiarities of the country, what they are and how many, in the same way that the mind forms its conceptions from the information of the senses. The figure, colour, and size of an apple, its scent, feel to the touch, and its flavour, are particulars communicated by the senses, from which the mind forms its conception of an apple. So in large figures, the senses observe the various parts, while the mind combines into one conception what is thus seen. And in like manner, men eager after knowledge, trusting to those who have been to various places, and to [the descriptions of] travellers in this or that country, gather into one sketch a view of the whole habitable earth. In the same way, the generals perform every thing, nevertheless, they are not present every where, but most of their success depends on others, since they are obliged to trust to messengers, and issue their commands in accordance with the reports of others. To pretend that those only can know who have themselves seen, is to deprive hearing of all confidence, which, after all, is a better servant of knowledge than sight itself. 12. Writers of the present day can describe with more certainty [than formerly] the Britons, the Germans, and the dwellers on either side of the Danube, the Getæ,[732] the Tyrigetæ, the Bastarnæ,[733] the tribes dwelling by the Caucasus, such as the Albanians and Iberians.[734] We are besides possessed of a description of Hyrcania[735] and Bactriana in the Histories of Parthia written by such men as Apollodorus of Artemita,[736] who have detailed the boundaries [of those countries] with greater accuracy than other geographers.