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XXI. Tables of Temperatures of the Sea at different Depths beneath the Surface , reduced 
and collated from the various observations made between the years 1749 and 1868, 
discussed. With Map and Sections. By Joseph Prestwich, M.A., F.B.S., F.G.S. 
Received May 14, — Read June 18, 1874. 
Contents. 
Page 
§ I. Introduction 587 
§ II. Historical Narrative of Deep-sea Observations, 1749-1868 590 
Ellis, Cook, Forster, Pbipps, Saussure, Peron, Krusenstern, Scoresby, Kotzebue, Wauch ope, Abel, 
John Ross, Parry, Sabine, Franklin, Emil. Lenz, Beechey, Blossville, D’Urville, FitzRoy, 
Graah, Berard, Du Petit-Tbouars, Yaillant, Martins and Bravais, Pratt, Wilkes, James Ross, 
Aime, Spratt, Belcber, Kellett, Dayman, Armstrong, Bacbe, Maury, Pullen, Wiillerstorf, 
Walker, Kiindson, Ed. Lenz, Wallicb, Shortland, Cbimmo. 
Methods of Observation employed, — tbeir Relative Merits 610 
Corrections for Pressure, — Du Petit-Tbouars, Martins, Aime, Miller 612 
§ III. Summary of tbe preceding Observations. 
Original opinions of Lenz and Du Petit-Thouars 613 
Opinions of D’Urville, James Ross, and Wilkes 614 
Maximum Density and Freezing-Point of Sea- water 616 
Corrected Reading of Temperatures in Tropical, Arctic, Antarctic, and Inland Seas 617 
§ IY. Hypotheses and Remarks of Humboldt, Arago, Lenz, and others 623 
§ V. General Conclusions. 
Different value of the old observations 630 
Position of the Bathymetrical Isotherms : — in the Atlantic from Spitzbergen and Baffin's Bay to 
the Antarctic Ocean ; in the Pacific from Behring’s Strait to the Antarctic Continent .... 631 
Undercurrents of Polar Waters : — their Rise in Equatorial Regions of the Atlantic 634 
Effects of the Polar deep undercurrents on the Oceanic surface-currents 635 
Inland Seas dependent on local Climatal Conditions 636 
Bearing of the subject on some Geological Problems 637 
Final Propositions 637 
Lists of Observations : — Northern Hemisphere ; Southern Hemisphere ; Inland Seas 639 
§ I. Introduction. 
This communication, the result of an inquiry having originally reference to the bearing 
of the subject on certain geological questions, was commenced more than twenty years 
ago, but abandoned for a time, partly owing to the pressure of other engagements, and 
partly waiting more accurate information of the range of life at depths*. The great 
impulse given to these questions by the more recent expeditions of the 4 Lightning ’ 
* A few of the geological questions were, however, noticed, and some of the early deep-sea temperature- 
observations given, in the author’s Anniversary Address to the Geological Society of February 1871, Quart. 
Journ. Geol. Soc. vol. xxvii. pp. xliii-lxxv. 
4 K 
MDCCCLXXV. 
