the outer port shaft was driven by a high-pressure turbine that exhausted into a medium pressure turbine driving the outer starboard shaft. the two middle shafts, capable of reversal, were each driven by a low-pressure turbine, which in emergencies could each be driven by exhaust from the high-pressure turbine. each shaft drove a four-bladed bronze propeller for a designed sea speed of 19 knots. steam was provided by six double-ended and four single-ended forced draft boilers divided between two boiler rooms. on trials in the clyde "calgarian" attained 21.25 knots and on a double run for contract speed made 20.63 knots, a knot and a half above required service speed.