On the Half Moon, we collect water samples the old-fashioned way: by simply heaving a tethered canvas bucket overboard and hauling it back on board.
These water samples are then collected in sample jars for analysis by the entire student crew as part of our Deck Log duties. We started this Voyage of Discovery well into the freshwater portion of the estuary, and will continue collecting samples until we reach the river's mouth at New York Harbor.
Students use a refractometer to measure salinity levels using refraction: the degree to which light bends as it passes through different materials. Saltier water bends light farther than fresher water, so a trained refractometer user can check salinity levels with just a glance. Sailors on board the original Half Moon in 1609 would have had to simply go by taste.
In addition to our Deck Log samples, on this Voyage of Discovery Bennett and Jonathan have chosen to study salinity for their student presentation. As we traveled down the Hudson, the crew took readings at every minute of latitude, the equivalent of one nautical mile. During our data layover at Grave's End Bay, Bennett and Jonathan also took readings every hour to track the tidal cycle.
Our results on this voyage were typical for our experiences; salt was first detected in the river off Beacon/Newburgh, rising steadily from there as we continued toward the ocean.