Take your time to read this article on Count Luigi Ferdinando Marsili’s Oceanoographic Cruise realized between 1679 and 1680. During this jurney the first in situ measurements of seawater density that referred to a geographical position at sea and time of the year were carried out in the Adriatic Sea, Aegean Sea, Marmara Sea, and the Bosporus. Not only was this the first investigation with documented oceanographic measurements carried out at stations, but the measurements were described in such an accurate way that the authors were able to reconstruct the observations in modern units.
The data reported in the historical oceanographic treatise Osservazioni intorno al Bosforo Tracio (Marsili) allowed the reconstruction of the sea water density at different geographic locations between 1679 and 1680
Marsili’s experimental methodology included the collection of surface and deep water samples, the analysis of the samples with a hydrostatic ampoule, and the use of a reference water to standardize the measurements.
Download the article: Measuring the Sea: Marsili’s Oceanographic Cruise (1679–80) and the Roots of Oceanography. Pinardi, N., E. Özsoy, M.A. Latif, F. Moroni, A. Grandi, G. Manzella, F. De Strobel, and V. Lyubartsev, 2018. J. Phys. Oceanogr., 48, 845–860, doi: 10.1175/JPO-D-17-0168.1