And following {33} in the spirit of the Greek thinkers themselves, modern students of antiquity have devoted themselves to eliciting the positive connection of conditions with history, up to a point of success of which the common run of modern sociologists appear to have no conception. When we reflect how typical and, comparatively speaking, how readily isolated and exhausted is the history of Ancient Greece in the greatest age, it seems extraordinary that the considerable and minute researches which have been bestowed upon its geographical, commercial, and economic conditions should not be commonly drawn into account with a view to the illustration of the relations between natural resources, commercial and economic development, and historical greatness. [1] [1] I have never, for example, seen the great work of Ernst Curtius, on the geography of the Peloponnese in connection with its historical development, referred to in any sociological treatise; nor, again, Duncker, nor Büchsenschütz, nor Mr. Newman’s edition of Aristotle’s _Politics_. Boeckh’s _Treatise on the Public Economy of Athens_ receives only a word of contemptuous notice in M’Culloch’s _Literature of Political Economy_. However this may be, here at any rate, in the analysis of economic and quasi-economic conditions in their bearing upon the life of peoples, we get a real subject-matter which is perhaps, so far as can yet be seen, the territory least disputably belonging to the pure sociologist. It is not really a sphere of natural causation, but it is a sphere of certain simple and general conditions in psychical life, corresponding to external facts which admit of more or less precise statement, and, we may hope, of reduction to fairly trustworthy uniformities. Such for instance are M. Durkheim’s investigations on the effect of {34} density of population upon the division of labour, [1] or Professor Gidding’s observations upon the causes and limiting conditions of the aggregation of populations. [2] We now proceed to a branch of experience which seriously strains the working conceptions of the sociologist. [1] _De la Division du Travail Social_, Alcan, 1893. [2] _Principles of Sociology_, bk. II., ch. i. Few things are more interesting in this respect than Mr. Poore’s observations in _Rural Hygiene_ on the mechanical conditions of modern city life, as regards drainage and water supply, with their results in encouraging an overcrowded and insanitary mode of living.