538 



Dr. W. B. Carpenter on the 



[June 13, 



Gravities by a graduated series of bulbs, adjusted to indicate differences of 

 O'l. On consulting Mr. Casella, I found him willing to undertake the con- 

 struction of such a series, which should range from 1025*0 to 1030 - 0. 

 These I have found to answer admirably, as the motion of a ship interferes 

 much less with their performance than it does with that of a delicate Hy- 

 drometer. — I should strongly recommend that a similar series, graduated 

 to every 0*2 (which is quite close enough for ordinary purposes), should 

 be provided for general use at sea, instead of the Hydrometers at present 

 furnished by the Meteorological Department. Every case of such bulbs 

 should include a small Thermometer suited for taking the exact temperature 

 of the water of which the Specific Gravity has to be ascertained, with a 

 Table whereby the observed Specific Gravity may be reduced to a common 

 standard — say 60°. In every observation, the Temperature should be care- 

 fully noted, and the requisite correction applied. I have strong reason to 

 believe that the neglect of such correction has led to no small exaggeration 

 of the differences between the Specific Gravities of the surface-water of 

 the Ocean in different regions*. The record of observations ought either 

 to state the result as corrected, or to state the Temperature at which each 

 Sp. Gr. determination, if uncorrected, was made. — In the present Report 

 all the Specific Gravities are reduced to the Standard of C0° Fahr. 



As it is not probable that I shall again take a personal share in the work 

 of Deep-sea Exploration, and as the present Report will therefore close the 

 account of the Physical inquiries which I have been led to consider as my 

 special department, I have thought it desirable to develope somewhat at 

 length what I regard as the bearings of the results obtained by these 

 inquiries upon the Doctrine of a General Oceanic Circulation sustained by 

 difference of Temperature. This has involved a careful examination of 

 the whole question of the Gulf-stream : as elucidated, on the one hand, by 

 the careful and elaborate Surveys prosecuted near the American Coast 

 under the able direction of the late Prof. Bache ; and, on the other, by the 

 Thermometric observations on the Surface-temperature of the Ocean, 

 which have been recently correlated as regards the Atlantic by our own 

 Hydrographic and Meteorological Departments, and as regards the Arctic 

 Sea by Dr. Petermann. As no similarly comprehensive examination has 

 been made, so far as I am aware, by any other scientific inquirer, and as the 

 doctrine put forth on the subject by Mr. Croll is likely, if not thus scruti- 

 nized, to command the unquestioning assent of those who regard him as 

 a high authority "on the subject of Oceanic Currents and their bearings on 

 Geological questions" f, I venture to hope that the inclusion of its results 

 as an Appendix to this Report will not be deemed inappropriate. 



* I cannot but think that there must be some such fallacy in the statement of Dr. 

 Rattray (Transact, of Linn. Soc. vol. xxvii. p. 272), that he encountered a range of 

 Specific Gravity in the Ocean-water of the Pacific from 1023| to 1029. 



t Address of the President of the Geological Society, 1872, p. xxviii. 



