before it issues from the last blades to the condenser.
Now as to the best speed of the blades, it will be easily seen that in order to obtain as much power as possible from a given quantity of steam, each row must work under appropriate conditions. This has been found by experiment to require that the velocity of the blades relatively to the guide blades shall be from one-half to three-quarters of the velocity of the steam passing through them, or more accurately equal to one-half to three-quarters of the velocity of issue from rest due to the drop of pressure in guides or moving blades, for in the usual reaction turbine the guides are identical with the moving blades.
The curve for efficiency in relation to the velocity ratio has a fairly flat top, so that the speed of the turbine may be varied considerably about that for maximum efficiency without materially affecting the result.
In compound land turbines the efficiency of the initial rows is about 60 per cent., and
