Canon Moseley on the steady Flow of a Liquid, 53 



over the surface of another. As the motions of the films over 

 one another are supposed uniform, the statical resistance must, 

 in respect of each, equal the pressure to which the film is sub- 

 jected in the direction of its motion and which causes it to move. 

 But this last is in every case given in amount; the former is 

 therefore also given in amount. It is this equivalent of //> which 

 comes in the place of /^_, and which eliminates it from the in- 

 quiry. Whence /x arises does not, therefore, come into question, 

 but only the fact that it exists, and is of that amount without 

 which the motion could not be uniform. 



I have now brought to an end the inquiries which I pro- 

 posed to myself. I have investigated the conditions of the 

 lateral propagation of motion in a liquid flowing from a reservoir 

 through a circular pipe, whose particles move parallel to one 

 another with a steady motion, to be represented by the equation 

 (see equation 13) 



where v^ is the maximum velocity of water flowing from the axis 

 of the pipe and 7 a quantity constant for the same pipe, what- 

 ever the ^ head of water, but variable for different dimensions of 

 the pipe and different conditions under which it receives the 

 water from the reservoir. 



From this equation I have deduced the discharge from such 

 a circular pipe per unit of time. It is given in terms of the 

 maximum velocity in equation (17). The discharge being known 

 in terms of the maximum velocity, it remained to determine the 

 maximum velocity itself under the given conditions of the dis- 

 charge. That is done by equation (29) ; while the absolute 

 value of the velocity is determined by equation (28), and the 

 discharge per 1" by equation (31); equations (39) and (40) de- 

 termine the same thing with respect to inclined pipes. Incidental 

 to these inquiries is that as to the work expended by water in 

 flowing through a pipe, and the rise of temperature due to that 

 expenditure of work. These are represented by equations (44) 

 and (45). 



These are the subjects of my two former papers. In the pre- 

 sent one I have investigated the general conditions of the lateral 

 propagation of motion in a liquid whose particles move parallel 

 to one another. It results from it that the particles move in 

 films geometrically similar to one another. It was the obvious 

 fact that when a liquid moves uniformly in a circular pipe which 

 it completely fills, its particles necessarily form themselves into 

 such films, which was the ground of the whole of my preceding 

 investigations. That _this principle, which is true of circular 

 pipes is true of pipes of all other forms of section, enables me to 



