ABSTRACT
This chapter talks about a composer, scientist, inventor, philosopher and Rear-Admiral Jean Cras was a French musician. But this French musician was also Proper Breton. Towards 1905, Jean Cras had begun finalizing the design for this navigational ruler-compass. There are two main uses for the Cras ruler-compass. If we already know the trajectory and have traced it on a navigational chart, we can find the bearing by making use of a meridian or a parallel. The Cras ruler-compass may also be used to trace a straight-line trajectory given the starting point and the direction. While keeping the point of departure on the edge of the ruler, we slide the ruler until the centre of the southernmost semi-circle coincides with a meridian or parallel.
