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PROFESSOR 0. REYNOLDS ON THE THEORY OF LUBRICATION 
On the left of GH the curves will be exactly similar to those on the right, only 
drawn the other way about, so that they are concave towards a section at P 2 in a 
similar position on the left to that occupied by P x on the right. 
This is because a uniformly varying motion would carry a quantity of fluid pro¬ 
portional to the thickness of the stratum from right to left, and thus while it would 
carry more fluid through the sections towards the right than it would carry across 
GH, necessitating an outward flow from the position P : in both directions, the same 
motion would carry more fluid away from sections towards C than it would supply 
past GH, thus necessitating an inward flow towards the position P 2 . 
Since G is in the middle of CD these two actions, though opposite, will be other¬ 
wise symmetrical, and 
P S G=GP 1 . 
From the convexity of the curves to the section at P 2 it appears that this section 
would be one of minimum pressure, just as P : is of maximum. Of course this is 
supposing the lubricant under sufficient pressure at C and D to allow of the pressure 
falling. The curve of pressure would be similar to that at the top of fig. 10, in which 
C and D are points of equal pressure, P 1 HP 3 the singular points in the curve. 
Under such conditions the fluid pressure acts to separate the surfaces on the right, 
but as the pressure is negative on the left the surfaces will be drawn together. So 
that the total effect will be to produce a turning moment on the surface AB. 
Case 6. The same as Case 5, except that G is not in the middle of CD. —In 
this case the curves of motion will be symmetrical on each side of H at equal 
distances, as shown in fig. 11. 
Fig. 11. 
If C lies between H and P 2 the pressure will be altogether positive, as shown by 
the curve above fig. 11 — that is, will tend to separate the surfaces. 
