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Several years more were spent by the author in the endeavour to discern these missing factors, but without success. Turning with disappointment from the subject of money, he sought an explanation of the vicissitudes of civilization in the development of natural resources. To this period belong his Essays on the Resources of Egypt, Spain, Prussia, 850. In two years' time he had completed and published either in pamphlets or magazine articles the industrial history of twenty countries, tracing it from the earliest times to the present. The result was unsatisfactory. There was evident correspondence between civilization and natural resources but it was imperfect. The development of these resources was sometimes but not always aecom panied by social advancement. The influence of nature is to encourage improvement. That mankind had not always improved was therefore no fault of nature: the cause must be sought in some neglected institution of man. It must be money, and yet the author's researches had failed to sustain this conjecture.
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