676 Memoranclitm on the Nevccistle Tinrjine T'rial,< 
pull on the upper ends of the adjusting levers begins to increase 
proportionately to the load added. This pull will have the 
effect of reducing the amount of the load on the brake by the 
amount of such pull reduced, in the ratio of the distance of the 
fixed ends of the levers from the centre of the brake shaft to 
the distance of the point of suspension of the load from the 
same place. 
I am indebted to my partner Mr. Wm. Dickinson for the 
following investigation into the theory of the brakes : — 
Let W = Load on brake strap. 
„ T, = Tensions just above and below the points of suspension of W. 
„ Tj Tj = Tensions at two ends 0 and D of strap connected to lower ends 
of compensating levers. 
„ P = Pull on upper ends of these levers. 
„ a, a' = lladii of brake strap and wheel rospectivelv. 
„ 0 B = d,(Jl) = b, and OE = o. 
„ F, = Friction of A ]5 C, 
„ Fj = Friction of A 1), and F = total friction of brake strap. 
The portion A li C of the brake strap is kept iu equilibrium by the 
