1872.] On the ' Shearwater' Scientific Researches. 



535 



" Report on Scientific Researches carried on during the Months of 

 August, September, and October, 1871, in H.M. Surveying- 

 ship ' Shearwater.'" By William B. Carpenter,LL.D., M.D., 



F.R.S. Received June 13, 1872. 



Introduction 535 



Part I. Temperature-Phenomena of the Atlantic, in relation to those of other Seas 



and to the G-eneral Oceanic Circulation . 539 



Part II. Further Investigation of the Gibraltar Currents 5G5 



Part III. Physical Eesearches in the Mediterranean 578 



Part IV. Biological Researches in the Mediterranean 587 



Appendix. 



I. On the Gulf-stream, in relation to the General Oceanic Circulation 592 



II. On the Dardanelles and Baltic Under-currents 638 



INTRODUCTION. 



As it was understood that the requirements of the Public Service would 

 not permit the employment, during any part of the last year (1871), of 

 either the 'Porcupine' or the 'Lightning/ for the continuation of the 

 Deep-sea Researches carried on by my Colleagues and myself in the three 

 preceding summers, it was not deemed advisable by us that the Council of 

 the Royal Society should be moved to make any application to the Ad- 

 miralty in furtherance of this object. Early in June, however, I was in- 

 formed by the Hydrographer that as the Surveying-ship ' Shearwater/ 

 under the command of Capt. Nares, was about to proceed to the Medi- 

 terranean, and would not be required to enter on her work until the end of 

 October, an opportunity would present itself for making further researches 

 on the Gibraltar Current, in which, if so disposed, I should have the ad- 

 vantage of being associated with Capt. Nares ; whilst, if inclined to proceed 

 as far as Egypt, I might have an opportunity of prosecuting in the Eastern 

 basin of the Mediterranean some of the Physical and Biological researches 

 which I had carried out last year in the Western. 



Although the results of the conjoint inquiries which had been made by 

 Capt. Calver and myself during the 'Porcupine' Expedition of 1870 

 seemed to us to leave no reasonable doubt as to the existence of an outward 

 Under-current in the Strait of Gibraltar, yet we both felt extremely desirous 

 that the matter should be more thoroughly examined ; for we were fully 

 conscious that the proof could not be regarded as complete, until direct 

 mechanical evidence should be obtained by the "current-drag" of the 

 passage of Mediterranean water over the " ridge " or " marine watershed " 

 between Capes Trafalgar and Spartel, which forms the proper boundary of 

 the Mediterranean basin, the evidence we had obtained of such passage 

 being inferential, and therefore open to objection. And as we saw, in 

 addition, that the rate, perhaps even the direction, of this under-current was 

 subject to variation under the influence of Winds and Tides, we felt that the 



vol. xx. 2 R 



