In order to achieve this Object, it is proposed in the first place to consider What is required Of a meter that it may efficiently discharge all its functions, then to examine the various types of meter dow obtainable, and to deter mine how far each one goes towards meeting those requirements. The next step will be to discuss the conditions incidental to the divers purposes for which these instruments are used, and lastly to suggest as impartially as possible the particular types of meter which best fulfil them. It is not intended to give any very technical formulae, Or diagrams Of loss of head, accuracy, etc., as such laboratory productions are of little worth as regards the end in view, whereas a short review Of the broad lines of actual fact.