Tens of thousands of samples of water have been taken from streams, springs, and wells for chemical analysis, without much use having been made of the results. Unfortunately, the chemists have been little concerned with any engineering interpretation of such analyses and the engineers have had no ready method of interpreting them. Consequently, engineers and agriculturists have usually limited themselves to consideration of only the total dissolved solids, or the total hardness, or possibly the amount of chlorides; the real significance of the analyses has been overlooked.