The parallel rules are used to plot courses, bearings, and celestial lines of position. By “walking” the rules across the chart, the navigator transfers the desired angle from the compass rose on the chart to the part of the chart where the ship is, or vice versa. A pair of triangles can do the same thing, while course plotters are designed to minimize effort in laying out angles.
Lobsterman getting traps ready in the spring. Traps have to be cleaned, dried, and repaired. This was especially hard work in the days of wooden traps, which rotted over time. Traps are being loaded onto a lobster boat that is just visible. A peapod is pulled out and set upside down on the nearby dock. Berry probaly took this photograph in New Harbor or Round Pond.
Each warp or line coming up from a pot or two on the bottom of the sea ends at a lobster pot buoy on the surface. Originally these buoys were cut with a hatchet from a small spruce trunk. Once laths became available, fishermen could turn buoys from larger pieces of wood. Small wood shops could make them in quantity for sale. Now buoys are hard foam.
Lobster measure, for measuring the carapace, or body shell, of the lobster. The shorter measure is 3 1/4", and that is the minimum allowable size of the carapace; the maximum is 5". If the lobster carapace is between these two lengths, and the lobster is not an egg-bearing female, it may be kept. Otherwise, the lobster must be thrown back. This measure has a float attached to it, so that it won't sink if dropped overboard.
Small wide rubber bands are used hold the large claws of the lobster closed, in order to keep lobsters from hurting each other when stored or shipped together. Before rubber bands, lobster fisherman whittled plugs that could be inserted into a lobster's claw to prevent them from opening.
This diagram shows important tools of the navigator for dead reckoning and piloting, including the lead line, chip log, a mechanical log, and a compass. For communications, speaking tubes are shown on the left. This illustration is from H. Paasch's Illustrated Marine Encyclopedia, 1890, Plate 98. For a 17th century navigator only the mechanical log would have been new.
Triangles provide a simple and inexpensive alternative to the parallel rule for transferring a bearing or course from the compass rose to the ship’s position on a chart. These triangles are made of wood.