Page:EB1911 - Volume 26.djvu/366

Rh ordinary crystalline dolerite, which in a very short distance may contain no vitreous base whatever. The spherulites may form the greater part of the mass, they may be a quarter of an inch in diameter and are occasionally much larger than this. These coarsely spherulitic rocks pass over into the variolites (q.v.) by increasing coarseness in the fibres of their spherulites, which soon become recognizable as needles of felspar or feathery growths of augite. The ultimate product of decomposition in this case also is a red palagonitic substance, but owing to the absence of steam cavities the tachylyte selvages of dikes are more often found in a fresh state than the basic lapilli in ash-beds. Many occurrences of basaltic pitchstones have been reported from Skye, Mull, and the western part of Scotland; they are found also in connexion with the intrusive dolerite sills of the north of England and the centre of Scotland. In the Saar district of Germany similar rocks occur, some of which have been described as weisselbergites (from Weisselberg).

Other localities for tachylytes of this group are Nassau, Silesia and Sweden.

The chemical composition of some of the rocks of this group is indicated by the analyses given below:—

 TACITUS, CORNELIUS (c. 55–120), Roman historian. Tacitus, who ranks beyond dispute in the highest place among men of letters of all ages, lived through the reigns of the emperors Nero, Galba, Otho, Vitellius, Vespasian, Titus, Domitian, Nerva and Trajan. All we know of his personal history is from allusions to himself in his own works, and from eleven letters addressed to him by his very intimate friend, the younger Pliny. The exact year of his birth is a matter of inference, but it may be approximately fixed near the close of the reign of Claudius. Pliny indeed, though himself born in 61 or 62, speaks of Tacitus and himself as being &ldquo;much of an age,&rdquo; but he must have been some years junior to his friend, who began, he tells us, his official life under Vespasian, no doubt as quaestor, and presumably tribune or aedile under Titus (80 or 81), at which time he must have been twenty-five years of age at least. Of his family and birthplace we know nothing certain; we can infer nothing from his name Cornelius, which was then very widely extended; but the fact of his early promotion seems to point to respectable antecedents, and it may be that his father was one Cornelius Tacitus, who had been a procurator in one of the divisions of Gaul, to whom allusion is made by the elder Pliny in his Natural History (vii. 76). But it is all matter of pure conjecture, as it also is whether his &ldquo;praenomen&rdquo; was Publius or Gaius. The most interesting facts about him to us are that he was an eminent pleader at the Roman bar, that he was an eye-witness of the &ldquo;reign of terror&rdquo; during the last three years of Domitian, and that he was the son-in-law of Julius Agricola. This honourable connexion, which testifies to his high moral character, may very possibly have accelerated his promotion, which he says was begun by Vespasian, augmented by Titus, and still further advanced by Domitian, under whom we find him presiding as praetor at the celebration of the secular games in 88, and a member of one of the old priestly colleges, to which good family was an almost indispensable passport. Next year, it seems, he left Rome, and was absent till 93 on some provincial business, and it is possible that in these four years he may have made the acquaintance of Germany and its peoples. His father-in-law died in the year of his return to Rome. In the concluding passage of his Life of Agricola he tells us plainly that he witnessed the judicial murders of many of Rome's best citizens from 93 to 96, and that being himself a senator he felt almost a guilty complicity in them. With the emperor Nerva's accession his life became bright and prosperous, and so it continued through the reign of Nerva's successor, Trajan, he himself, in the opening

passage of his Agricola, describing this as a &ldquo;singularly blessed time,&rdquo; but the hideous reign of terror had stamped itself ineffaceably on his soul, and when he sat down to write his History he could see little but the darkest side of imperialism. To his friend the younger Pliny we are indebted for the little we know about his later life. He was advanced to the consulship in 97, in succession to a highly distinguished man, Verginius Rufus, on whom he delivered in the senate a funeral eulogy. In 99 he was associated with Pliny in the prosecution of a great political offender, Marius Priscus, under whom the provincials of Africa had suffered grievous wrongs. The prosecution was successful, and both Tacitus and Pliny received a special vote of thanks from the senate for their conduct of the case. It would seem that Tacitus lived to the close of Trajan's reign, as he seems to hint at that emperor's extension of the empire by his successful Eastern campaigns from 115 to 117. Whether he outlived Trajan is matter of conjecture. It is worth noticing that the emperor Tacitus in the 3rd century claimed descent from him, and directed that ten copies of his works should be made every year and deposited in the public libraries. He also had a tomb built to his memory, which was destroyed by order of Pope Pius V. in the latter part of the 16th century.

Pliny, as we see clearly from several passages in his letters, had the highest opinion of his friend's ability and worth. He consults him about a school which he thinks of establishing at Comum (Como), his birthplace, and asks him to look out for suitable teachers and professors. And he pays him the high compliment, &ldquo;I know that your Histories will be immortal, and this makes me the more anxious that my name should appear in them.&rdquo;

The following is a list of Tacitus's remaining works, arranged in their probable chronological order, which may be approximately inferred from internal evidence: &mdash; (1) the Dialogue on Orators, about 76 or 77; (2) the Life of Agricola, 97 or 98; (3) the Germany, 98, published probably in 99; (4) the Histories (Historiae), completed probably by 115 or 116, the last years of Trajan's reign (he must have been at work on them for many years); (5) the Annals, his latest work probably, written in part perhaps along with the Histories, and completed subsequently to Trajan's reign, which he may very well have outlived.

The Dialogue on Orators discusses, in the form of a conversation which Tacitus professes to have heard (as a young man) between some eminent men at the Roman bar, the causes of the decay of eloquence under the empire. There are some interesting remarks in it on the change for the worse that had taken place in the education of Roman lads. The style of the Dialogue is far more Ciceronian than that of Tacitus's later work, and critics have attributed it to Quintilian; but its genuineness is now generally accepted. It is noticeable that the mannerisms of Tacitus appear to develop through his lifetime, and are most strongly marked in his latest books, the Annals.

The Life of Agricola, short as it is, has always been considered an admirable specimen of biography. The great man with all his grace and dignity is brought vividly before us, and the sketch we have of the history of our island under the Romans gives a special interest to this little work.

The Germany, the full title of which is &ldquo;Concerning the geography, the manners and customs, and the tribes of Germany,&rdquo; describes with many suggestive hints the general