TWO monographs dealing with the properties of solutions have recently been issued by the, Carnegie Institution of Washington. The first, entitled “Osmotic Pressure of Aqueous Solutions,” is a report by H. N. Morse, on the investigations made, in the chemical laboratory of the Johns Hopkins University during the years 1899-1913. This masterly investigation, extended already over a period of fifteen years, has been recognised at once, and universally, as one of the classics of scientific literature. As the substance of the investigation was originally issued in more than a score of papers, it is a great advantage to have the whole work summarised, corrected, and brought up to date by the author himself. The whole technique is now set out in a series of chapters dealing with the cells and manometer attachments; the manometers; the regulation of temperature; and the membranes. The fifth chapter contains a strong defence of the weight-normal system for solutions against criticisms and attacks that have been made upon it,—arising mainly from the mistaken assumption that this method of working was the expression of some theoretical view of the nature of solutions or the mechanism of osmotic pressure.