BOOK IV

This section of the treatise begins with a denunciation of flattery and ends with another against luxury. Neither the preface nor the concluding chapter have any obvious connection with the text between them. It is curious to note that while Seneca here warns his friend Lucilius against flatterers, and inculcates how their approaches are to be met, he himself in this very volume perpetrates four pieces of flattery to the despicable but all-powerful Nero. He quotes a prosaic line from a poem of the emperor’s, which he characterises as “most elegant” (_disertissime_, 25). He refers to Nero as most devoted to truth as well as to the other virtues (235); he refers to the advent of a comet which appearing in Nero’s reign had redeemed these heavenly bodies from their evil repute (290), and he describes that reign as “most joyous” (_laetissimus_, 294). The old courtier, so long habituated to the language of flattery, was perhaps hardly conscious that he was here making use of it, or he may naturally have reflected that at a time when the emperor had ceased to bear him any good will, the absence of the customary adulation might cause as much offence as if a direct insult were intended.

When from his ethical lecture he turns to resume his physical disquisitions, it is the mysterious Nile to which he devotes attention. After a brief contradiction of the statement of some philosophers that the Nile and the Danube are similar in their characters, he enumerates some of the well-known peculiarities of the river of Egypt. A problem which greatly exercised the minds of the philosophers of antiquity, and which has only been finally solved in our own day, was the cause of the annual rise of the Nile on which the fertility of Egypt depended. Seneca says with justice that if the point of the river could be ascertained where the rise begins the question would be settled. He does not appear to have known much about the river, for he believed that the water is for the first time collected into a single channel at Philae. In his account of that place and of the cataract there (168, 169), he speaks of the river’s egress from Ethiopia, and of deserts which are crossed by the trade route to the Red Sea. In a subsequent part of the treatise he gives the interesting and important information that he had himself seen and conversed with two centurions who had been despatched by Nero to discover the source of the Nile (235). From them he learnt that they had penetrated far into the heart of Africa, and had reached a region of illimitable marshes where the river was so covered and impeded with vegetation that neither on foot nor by boat could it be ascended. There can be no doubt that these enterprising explorers had come to the _sudd_, which in recent years has been found so serious an impediment to navigation. They informed Seneca that in the marsh region they had seen with their own eyes “two rocks from which an enormous body of the river came out.” There are apparently no rocks along the course of the Nile in the present marsh region, which is a vast flat, and it is therefore difficult to conjecture to what the two military surveyors allude. Possibly they saw the mouth of some affluent of the main stream such as the Khor Adar, or the _sudd_ may have extended further north than it does now.

Seneca’s account of the Nile derived from travellers and previous writers gives a clear summary of what was then known about the river, but of more interest is his discussion of the opinions that had been propounded before his time as to the cause of the annual rise. He first quotes the view of Anaxagoras, shared by the Greek tragedians and widely accepted, that this rise was due to the melting of snow on the uplands of Ethiopia. This idea he cogently combats by adducing various kinds of evidence of the great warmth of the climate in those southern regions. Some of these proofs, indeed, are exaggerations, as where he affirms that silver is unsoldered or melted. But one of his proofs, drawn from the habits of the animals of the country, is worthy of notice. He remarks that no hibernating creature is found there, and that even in midwinter the serpent is seen above ground. He argues that in Africa, as in Europe, melting snow would swell the rivers in spring and early summer, whereas the Nile flood continues to rise later during four months.

In a subsequent part of this treatise (235) allusion is made to an explanation which had been given of the rise of the Nile, that it is due not to the fall of rain from above but to the outflow of water from within the earth, and it is in connection with this opinion that he cites the experience of Nero’s two centurions above referred to, as if he were disposed to believe that what these explorers saw was really a vast body of water issuing from underground.

The opinion of Thales is next criticised that the Etesian or northerly winds drive the waters of the Mediterranean against the mouths of the Nile and consequently pond back the waters of the river. This view was of course entirely erroneous, but though Seneca rejects it, he does not seem to have quite understood it, for he argues that, coming from the same quarter as the winds, the Nile water should not have been turbid, but clear and blue, like that of the sea. In commenting upon the futile support given by Euthymenes of Marseilles to the idea of Thales, Seneca throws light on the wide extent to which the coasts of the outer sea had then been made known by trading vessels.

In rejecting another explanation proposed by Oenopides of Chios, the author shows that he is aware of the fact that caves and wells are warm in winter and cool in summer, and that he has partly divined the reason, when he states that in winter they are warm since they do not admit the frosty air from without and in summer they feel cold because the warm air from outside has not penetrated into their recesses. He returns to this subject in Book VI. (241).[115]

[115] The various ancient interpretations of the cause of the Nile’s annual rise are succinctly given by Lucretius (_De Rer. Nat._ vi. 712–37), but he does not indicate a preference for any one in particular, though he devotes most space to the influence of the Etesian winds.

After mentioning and dismissing a grotesque suggestion of Diogenes of Apollonia, Seneca suddenly drops the discussion of the Nile and passes on to the subject of hail. It is obvious that there is here a serious gap in the text. It is not probable that he meant to leave off his examination into the probable sources of the Nile without stating his own view of a matter which had been so long the subject of wonder and debate. Either, therefore, he never completed this section of his treatise, or a portion of the work has been lost.

The remainder of Book IV. is taken up with a desultory discussion of the subjects of hail and snow, written when the author must have been in a somewhat frivolous mood. He begins by telling Lucilius that if he were to assert that hail is produced as ice is with us, a whole cloud being frozen, he would be rather audacious. So he will imitate the chroniclers, who after they have told a great many lies, refuse to be responsible for some one statement, and refer for its truth to the authorities. If, therefore, his friend doubts his word, he will call in Posidonius, who will tell him that hail is formed from a watery cloud just turned into liquid. No teacher is needed to explain why pellets of hail are round, for all drops take that shape. Hail is nothing else than suspended ice, and snow is suspended hoar-frost. In this light vein Seneca thinks he has finished the subject and might dismiss it, but he cannot resist the temptation to continue the persiflage a little further. He quotes in a bantering style some of the opinions of his brother Stoics, and after this long preamble begins an inquiry into the distribution of density and temperature in the atmosphere.

It would have been interesting had he seriously and fully stated what was known or surmised on this last topic, but he dismisses it in three short chapters. We learn from these that he regarded the air to be densest next the earth, and that as all things retain heat better the denser and more compact they are, so the air becomes less warm in proportion to its height (184).[116] The opinion of some persons, that the air on mountain summits ought to be warmer because they are nearer the sun, is sagaciously controverted, and the insignificance of all inequalities on the surface of the earth in comparison with the distance from the earth to the sun is forcibly expressed and illustrated.

[116] This view hardly agrees with what is expressed in Book II. (60, 61), but it more accurately expresses the fact.

The subject of snow and hail is briefly reintroduced at the end of the Book, probably for the purpose of affording a convenient introduction to the invective against luxury which fills the concluding chapter. The preservation of snow in ice-houses, and its use in the reparation of jaded appetites by cooling drinks, calls forth a denunciation of the young rakes of his day, which closes the discussion.