150 years of Challenger Expedition

150 years ago, on 21 December 1872, HMS Challenger sailed from Portsmouth, England, on the first expedition organized and funded for a specific scientific purpose. One of the major tasks of the expedition was to take samples at several depths over all of the oceans and to bring these samples back to England for complete chemical analysis. The results of analyses of collected 77 samples led to the establishment of the law of the constant proportion of the major chemical constituents of seawater in all oceans. “The importance of this result cannot be over-emphasized, as upon it depends on the validity of chlorinity-salinity-density relationship and, hence, the accuracy of all conclusions based on the distribution of density where the latter is determined by chemical or indirect physical methods, such as electrical conductivity…” Sverdrup, Johnson, Fleming “The Oceans”