In tracing the intellectual progress of mankind and the gradual extension of cosmical views, the period of the Roman universal Empire presents itself as one of the most important epochs. We now for the first time find all those fertile regions of the globe which surround the basin of the Mediterranean connected in a bond of close political union, which also comprehended extensive countries to the eastward. I may here appropriately notice, that this political union gives to the picture which I endeavour to trace, (that of the history of the contemplation of the universe), an objective unity of presentation. Our civilization, i. e. the intellectual development of all the nations of the European Continent, may be regarded as based on that of the dwellers around the Mediterranean, and more immediately on that of the Greeks and the Romans. That which we term, perhaps too exclusively, classical literature, has received this denomination through men's recognition of the source from whence our earliest know ledge has largely flowed, and which gave the first impulse to a class of ideas and feelings most intimately connected with the civilization and intellectual elevation of a nation or a race. We do not by any means regard as unimportant the elements of knowledge, which, flowing through the great current of Greek and Roman cultivation, were yet derived in a variety of ways from other sources—from the valley of the Nile, Phœnicia, the banks of the Euphrates, and India; but even for these we are indebted, in the first instance, to the Greeks, and to Romans surrounded by Etruscans and Greeks.

In my sketch of the history of the physical contemplation of the universe, I have already enumerated four leading epochs in the gradual development of the recognition of the universe as a whole. These included, firstly, the period when the inhabitants of the coasts of the Mediterranean endeavoured to penetrate eastward to the Euxine and the Phasis, southward to Ophir and the tropical gold lands, and westward through the Pillars of Hercules into the “all-surrounding ocean;” secondly, the epoch of the Macedonian expeditions under Alexander the Great; thirdly, the period of the Lagidæ; and fourthly, that of the Roman Empire of the World. We have now to consider the powerful influence exercised by the Arabians, whose civilization was a new element foreign to that of Europe,—and, six or seven centuries later, by the maritime discoveries of the Portuguese and Spaniards,—on the general physical and mathematical knowledge of nature, in respect to form and measurement on the earth and in the regions of space, to the heterogeneity of substances, and to the powers or forces resident therein. The discovery and exploration of the New Continent, with its lofty Cordilleras and their numerous volcanoes, its elevated plateaus with successive stages of climate placed one above another, and its various vegetation ranging through 120 degrees of latitude, mark incontestably the period in which there was offered to the human mind, in the smallest space of time, the greatest abundance of new physical perceptions.

The Macedonian Expeditions under Alexander the Great, the downfal of the Persian Empire, the beginning of intercourse with Western India, and the influence of the 116 years' duration of the Greco-Bactrian kingdom, mark one of the most important epochs of General History; or of that part of the progressive development of the History of the Human Race, which treats of the more intimate communication and union of the European countries of the West with South-Western Asia, the Valley of the Nile and Lybia. The sphere of the development of community of life, or of the common action and mutual influence of different nations, was not only immensely enlarged in material space, but it was also powerfully strengthened, and its moral grandeur increased, by the constant tendency of the unceasing efforts of the conqueror towards a blending of all the different races, and the formation of a general unity, under the animating influences of the Grecian spirit. The foundation of so many new cities at points the selection of which indicates higher and more general aims, the formation and arrangement of an independent community for the government of those cities, the tenderness of treatment towards national usages and native worship, all testify that the plan for a great organic whole was laid. At a later period, as is always the case, much which may not have been originally comprehended in the plan, developed itself from the nature of the relations established.

It has often been said, that if delight in nature were not altogether unknown to the ancients, yet that its expression was more rare and less animated among them than in modern times. Schiller, in his considerations on naïve and sentimental poetry, remarks, that “when we think of the glorious scenery which surrounded the ancient Greeks, and remember the free and constant intercourse with nature in which their happier skies enabled them to live, as well as how much more accordant their manners, their habits of feeling, and their modes of representation, were with the simplicity of nature, of which their poetic works convey so true an impress, we cannot but remark with surprise how few traces we find amongst them of the sentimental interest with which we moderns attach ourselves to natural scenes and objects. In the description of these, the Greek is indeed in the highest degree exact, faithful, and circumstantial, but without exhibiting more warmth of sympathy than in treating of a garment, a shield, or of a suit of armour. Nature appears to interest his understanding rather than his feelings; he does not cling to her with intimate affection and sweet melancholy, as do the moderns.”

In attempting to recount the most distinctly marked periods and gradations of the development of cosmical contemplation, we have in the last section endeavoured to depict the epoch, in which one hemisphere of the globe first became known to the cultivated nations inhabiting the other. The epoch of the most extensive discoveries upon the surface of our planet was immediately succeeded by man's first taking possession of a considerable part of the celestial spaces by the telescope. The application of a newly formed organ, of an instrument of space-penetrating power, called forth a new world of ideas. Now began a brilliant age of astronomy and mathematics; and in the latter the long series of profound investigators, leading to the “all-transforming” Leonard Euler, the year of whose birth (1707) is so near the year of Jacob Bernouilli's death.

A few names may suffice to recal the giant strides with which the human mind advanced in the 17th century, less from any outward incitements than from its own independent energies, and especially in the development of mathematical thought. The laws that regulate the fall of bodies, and the planetary motions, were recognised; the pressure of the atmosphere, the propagation of light, and its refraction and polarisation, were investigated. Mathematico-physical science was created, and established on firm foundations.

After the dissolution of the great Macedonian Empire comprising territories in the three Continents, the germs which the uniting and combining system of the government of Alexander had deposited in a fruitful soil, began to develop themselves every where, although with much diversity of form. In proportion as the national exclusiveness of the Hellenic character of thought vanished, and its creative inspiring power was less strikingly characterised by depth and intensity, increasing progress was made in the knowledge of the connection of phenomena, by a more animated and more extensive intercourse between nations, as well as by a generalisation of the views of Nature based on argumentative considerations. In the Syrian kingdom, by the Attalidæ of Pergamos, and under the Seleucidæ and the Ptolemies, this progress was favoured and promoted every where and almost at the same time by distinguished sovereigns. Grecian Egypt enjoyed the advantage of political unity, as well as that of geographical position; the influx of the Red Sea through the Straits of Bab-el-Mandeb to Suez and Akaba, (occupying one of the SSE.-NNW. fissures, of which I have elsewhere spoken), bringing the traffic and intercourse of the Indian Ocean within a few miles of the coasts of the Mediterranean.

The kingdom of the Seleucidæ did not enjoy the advantages of sea traffic, which the distribution of land and water, and the configuration of the coast line, offered to that of the Lagidæ; and its stability was endangered by the divisions produced by the diversity of the nations of which the different Satrapies were composed.