We, therefore, conclude that the function of government in disaster is of primary importance, and that social legislation when forthcoming constitutes an important and deciding influence and is itself in turn enriched by calamity. Brought to the test of comparison with observed facts the statement in the Introduction, that catastrophe is in close association with progress in social legislation receives abundant justification. CHAPTER VII CATASTROPHE AND SOCIAL SURPLUS Mill's explanation of the rapidity with which communities recover from disaster--The case of San Francisco--The case of Halifax--Social surplus--The equipmental factors--Correlation of tragedy in catastrophe with generosity of public response--Catastrophe insurance--A practical step. John Stuart Mill offers a very interesting explanation of what has so often created wonder, the great rapidity with which countries recover from a state of devastation, the disappearance in a short time of all traces of the mischiefs done by earthquakes, floods, hurricanes and the ravages of war.[143] This "_vis medicatrix naturae_" he explains on an economic principle. All the wealth destroyed was merely the rapid consumption of what had been produced previously, and which would have in due course been consumed anyway. The rapid repairs of disasters mainly depends, he says, on whether the community has been depopulated. [143] Mill, John Stuart, _Principles of Political Economy_ (London, 1917), ch. v, p. 74. But this is not an all-sufficient explanation, and indeed applies particularly to countries which have not been bereft of the raw materials of industrial machinery. San Francisco recovered exceedingly rapidly from her terrible experience of 1906. Indeed her quick recovery has been called one of the wonders of the age. San Francisco was not depopulated. Her actual losses of life were but four hundred and ninety-eight, and those injured four hundred and fifteen. The loss of life on the other hand was about two thousand in Halifax, a city of fifty thousand population--but one-eighth that of San Francisco--and her list of injured ran into many thousands. And yet the same phenomenon appeared.