The use of water as a motive power has been so well known from the earliest ages of which we have any record, and the best mode of its application has formed the subject of so many' scientific treatises, that the Author feels he cannot advance any new views, or establish any new rules of construction of the more ancient forms of wheels. Modern inventions for utilising the impulsive power of water, such as turbines, do not seem however, to have been thoroughly investigated; at least, the Author has not been able to meet with any treatise, in which detailed rules of con struction have been given; or if detailed rules of construction have been given, no scientific reason has been laid down for their adoption.