MONEY 135 irregular way. A degree of periodicity seems to rule in the midst of much irregularity. It usually happens that an interval of some seven, or ten and - a half years, or there abouts, intervenes between the culminating points of two periods of bad trade. The explanation of this curious circumstance has been attempted by many economists, but it cannot be said that as yet it has been quite satisfactorily accounted for. Some incline to attribute it to a cyclical variation in the seasons which affect harvests ; but the nature of this variation, if it exists, is still obscure. Others are disposed to assume implicitly or explicitly that there is a cyclical movement in what may be called the social mind or the public attitude to affairs ; and yet others imagine that under competition the rivalry of indi vidual producers with one another auto matically induces over-production for which collapse is the unavoidable penalty. Which of these causes are real and which really count has not been conclusively determined hitherto ; and our purpose now that we are dealing with the matter of money is not to discuss them but to consider how trade oscillations are and can be influenced by the operations of banks in the way of restricting or enlarging the credit media of exchange.