AND ITS APPLICATION TO MR. B. TOWER’S EXPERIMENTS. 
183 
This appears to offer a very simple and well-founded explanation of the important 
and common circumstance that new surfaces do not behave so well as old ones; and of 
the circumstance, observed by Mr. Tower, that in the case of the oil hath, running the 
journal in one direction does not prepare the brass for carrying a load when the journal 
is run in the opposite direction. This explanation, however, depends on the effect 
of misfit in the journal and brass which has yet to be considered. 
Case 10. Approximately cylindrical surfaces of limited, length in the direction of the 
axis of rotation. —Nothing has so far been said of any possible motion of the fluid 
perpendicular to the direction of motion and parallel to the axis of the journal. It 
having been assumed that the surfaces were truly cylindrical and of unlimited 
length in direction of their axes, and in such case there would be no such flow. 
But in practice brasses are necessarily of limited length, so that the oil can escape 
from the ends of the brass. Such escape will obviously prevent the pressure of the 
film of oil from reaching its full height for some distance from the ends of the brass 
and cause it to fall to nothing at the extreme ends. 
This was shown by Mr. Tower, who measured the pressure at several points along 
the brass in the line through 0, and found it to follow a curve similar to that shown 
in fig. 15, which corresponds to what might be expected from escape at the free ends. 
Fig. 15. 
Ii the surfaces are not strictly parallel in the directions TU and YW, the pressure 
would be greatest in the narrowest parts, causing axial flow from those into the broader 
spaces. Hence, if the surfaces were considerably irregular, the lubricant would, by 
