one-third of the
time.

2. That each sectional blade exerts the equivalent efficiency of the
first or entering third portion of the breadth of an ordinary
propeller blade, and that consequently the combined sections have
greater effective power. It is now regarded by experts as an
ascertained fact that the after or trailing portion of the broad blade
is relatively non-effective as compared with the forward or entering
portion.

3. When three blades are fitted, the spent water from No. 2 being
delivered immediately in the wake of No. 3, and that from No. 1 in the
wake of No. 2, has the effect of destroying or reducing to a minimum
the back draught of sections Nos. 2 and 3, No. 1 alone being subject
to this drawback. This is of greater importance than might at first
thought appear, as in cases where there are three or four blades
revolving in one plane, the water is drawn after the retreating blade,
lessening the resistance to the face of the advancing one.

4. That by the subdivision of the blades, as arranged spirally, the
water passing through within the radius of the propeller has its
resisting capacity more thoroughly worked out than is possible with
any propeller whose blades are all on the same plane. This view is
confirmed by the visibly increased rotation of the water in the wake
of the vessel.

5. That by broadening the blades or increasing the number of sections,
the diameter of the propeller may be proportionately diminished
without the sacrifice of engine power. This is often desirable with
vessels of light draught, the complete immersion of the screw being at
all times necessary to avoid waste of power.

6. The propeller being made and fitted on the shaft in sections, all
that is necessary in case of accident is to replace the broken
section. This in many cases could be done afloat.

7. The blades being arranged to take their water at different planes,
there is the greater certainty of one or other of the sections
operating upon what is termed the water of friction. This is
considered an advantage.

8. Where it is desirable, the blades of the different sections can be
made of varying breadth or pitch.

9. The principle of division into two or more sections applies equally
to two, three, or four bladed ordinary propellers.

10. The adoption of this principle does not entail any alteration or
enlargement of the screw space or bay as usually provided.

11. As a consequence of the freedom and rapi