Abstract This paper is in the nature of a preliminary announcement describing the development of a new type of water-wheel runner which on account of its greater speed and lower cost is expected to largely supplant the well-known mixed-flow reaction (Francis) types of runners under low-head conditions. The radical nature of such a departure from accepted practice may be realized when it is considered that, except for the earliest stages of water-wheel development about the middle of the last century, the mixed-flow reaction runner has been accepted as being without an equal for low-head work. This paper has accordingly been prepared with the idea of showing briefly what the general trend of design has been from the date of the first turbines, which were built in about 1830, until the development and perfection of the mixed-flow runner, dating perhaps from 1860 to the present time, and to point out and discuss the radical nature of the departure from this latter practice in the design of the new type. In order to provide a simple criterion of progress, but particularly to afford a more ready means of contrasting previous practice with the development described, the first part of the paper is devoted to an explanation of the term “characteristic speed” and its applications. This explanation, while in the nature of a repetition of much more extensive articles previously written, is thought to be desirable by reason of its peculiar adaptability to water-wheel analysis, and because it is not in as common use among engineers in general as it might be. A brief history of water-wheel development is likewise given, based on a consideration of characteristic speeds attained by successive types and during different periods of development. This history is brought up to date and includes the origin and development of the new type of runner. Briefly this history indicates that for nearly one hundred years characteristic speeds were gradually increased from 20 to 100, whereas the new form of runner with its greater simplicity and flexibility reaches characteristic speeds averaging 150, which thus permits it to attain speeds over 50 per cent greater than possible with preceding types. Finally a brief statement of the advantages and field of application of the new type is given, showing that by its use it is possible to build satisfactory machinery for heads down to one-half those previously found to be the limit, and for present head limits to go to over double the capacity of units previously used.