originating the laws of international values, yet they are but a development of Ricardo's doctrine of international trade, and Mill's discussions of the progress of society toward the stationary state were also hinted at, although obscurely, by Ricardo. In the volumes of Mr. Mill the subject is developed as symmetrically as a proof in geometry. While he held strongly to free trade,45 he gave little space to the subject in his book. All in all, his book yet remains the best systematic treatise in the English language, although much has been done since his day.46
He who has improved upon previous conceptions, and been the only one to make any very important advance in the science since Mill's day, is J. E. Cairnes,47 in his “Leading Principles of [pg 024] Political Economy newly expounded” (1874). Scarcely any previous writer has equaled him in logical clearness, originality, insight into economic phenomena, and lucidity of style. He subjected value, supply and demand, cost of production, and international trade, to a rigid investigation, which has given us actual additions to our knowledge of the study. The wages-fund theory was re-examined, and was stated in a new form, although Mr. Mill had given it up. Cairnes undoubtedly has given it its best statement. His argument on free trade (Part III, chapter iv) is the ablest and strongest to be found in modern writers. This volume is, however, not a systematic treatise on all the principles of political economy; but no student can properly pass by