162 
PROFESSOR O. REYNOLDS ON THE THEORY OF LUBRICATION 
brasses used was '00077 inch greater than that of the journal, while at a temperature 
of 70° Fa.hr. that of the other was ‘00084 inch, or 9 per cent, larger than the first. 
These two brasses w r ere probably both bedded to the journal in the same way, and 
had neither of them been subjected to any great amount of wear, so that there is 
nothing surprising in their being so nearly the same fit. It would be extremely 
interesting to find whether prolonged wear of the brass tends to preserve or destroy 
the fit. This does not appear from Mr. Tower’s experiments. It does appear, 
however, that the brass expands with an increase of temperature more than the 
journal, and that its radius increases as the load increases in a very definite manner. 
Another circumstance brought out by the theory, and remarked on both by Lord 
IIayleigk and the author at Montreal, but not before expected, is that the point of 
nearest approach of the journal to the brass is not by any means in the line of the 
load, and, what is still more contrary to common supposition, is on the off * side of 
the line of load. 
This circumstance, the reason for which is rendered perfectly clear by the conditions 
of equilibrium, at once accounts for a singular phenomena mentioned by Mr. Tower, 
viz., that the journal having been run in one direction until the initial tendency to 
heat had entirely disappeared, on being reversed it immediately began to heat again; 
but this effect stopped when the process had been often repeated. The fact being 
that running in one direction the brass had been worn to the journal only on the off 
side for that direction, so that when the motion was reversed the new off side was 
like a new brass. 
7a. The circumstances which determine the greatest load which a bearino’ will 
carry with complete lubrication, i.e,, with the film of oil extending between brass and 
journal throughout the entire arc, are definitely shown in the theory. 
The effect of increasing the load beyond a certain small value being to cause the 
brass to approach nearer to the journal at a point II which moves from A towards O as 
the load increases, and when the load is such that the least separating distance ca is 
about half the difference of radii a, the angular position of H is 40° to the off side of O, 
the middle of the brass. At this point the pressure in the oil film is everywhere greater 
than at A and B, the extremities of the brass, but when the load further increases the 
pressure towards A on the off side becomes smaller or negative. This when sufficient 
* “ On” and “ off ” sides of the line of load are nsed by Mr. Tower to express respectively the sides of 
approach and succession, as B and A in the figure, the arrow indicating the direction of rotation. 
