This latter part, however, of the Commentaries of Hirtius, has been lost, as it seems now to be generally acknowledged that he was not the author of the book _De Bello Hispanico_, which relates Cæsar’s second campaign in Spain, undertaken against young Cneius Pompey, who, having assembled, in the ulterior province of that country, those of his father’s party who had survived the disasters in Thessaly and Africa, and being joined by some of the native states, presented a formidable resistance to the power of Cæsar, till his hopes were terminated by the decisive battle of Munda. Dodwell, indeed, in a Dissertation on this subject, maintains, that it was originally written by Hirtius, but was interpolated by Julius Celsus, a Constantinopolitan writer of the 6th or 7th century. Vossius, however, whose opinion is that more commonly received, attributes it to Caius Oppius(219), who wrote the Lives of Illustrious Captains, and also a book to prove that the Ægyptian Cæsario was not the son of Cæsar. Oppius was Cæsar’s confidential friend, and companion in many of his enterprizes; and it was to him, as we are informed by Suetonius, that Cæsar gave up the only apartment at an inn, while they were travelling in Gaul, and lay himself on the ground, and in the open air(220). A fragment has been added at the end of this book, on the Spanish war, by Jungerman, from a MS. of Petavius. Vossius thinks that this fragment was taken from the Commentaries, called those of Julius Celsus, on the Life of Cæsar, published in 1473. These Commentaries, however, were the work of a Christian writer; but Julius Celsus, a Constantinopolitan of the 6th century, already mentioned, having revised the Commentaries of Cæsar, the work on his life came, (from the confusion of names, or perhaps from a fiction devised, to give the stamp of authority,) to be attributed to Julius Celsus, who was contemporary with Cæsar, and was reported to have written a history of his campaigns; just in the same way as a fabulous life of Alexander, produced in the middle ages, passes to this day under the name of Callisthenes, the historiographer of the Macedonian monarch.