Physical Conditions of Inland Seas. 545 



I would observe, in conclusion, that, although much has been 

 •written on the geology of Arran, comparatively little is accurately 

 known, especially as regards the rocks in the southern half of the 

 island. A few rambles along the shore and among the hills should 

 surely teach a geologist that there are igneous rocks of different ages, 

 presenting various modes of occurrence; yet such important dis- 

 tinctions as those between interbedded sheets and intrusive dykes 

 have been generally overlooked or completely misunderstood. What 

 is now wanted is a good geological map and memoir, a work which 

 could not be in better hands than in those of Prof. Greikie and his 

 staff, and with which it is to be hoped geologists may soon be 

 favoured. 



V. — On the Temperature and other Physical Conditions of 



Inland Seas, in their Eelation to Geological Inquiry.^ 



By William B. Carpenter, M.D., LL.D., F.R.S., F.G.S. 



THE fesearches in which the Author has been personally engaged during the last 

 four years into the Temperature and other Physical conditions of the Deep Sea, 

 combined with the information he has obtained from other sources, have led him to 

 the knowledge of certain remarkable differences in regard to these conditions, -which 

 prevail between Inland Seas and the open Ocean. As these dift'erences have a most 

 direct and important bearing upon the distribution of Animal life, and as it would 

 seem highly probable that similar diiferences have existed in all Geological periods, 

 he thinks it important that Geologists, by being made aware of them, should be in 

 possession of a key that seems likely to open the way to a rational interpretation of 

 many Palseontological phenomena which are at present obscure. 



The general facts in regard to Ocean Temperature, which have been determined by 

 recent observations, are briefly as follows : — 



1. In high Northern latitudes, the Temperature of the surface of the sea, near the 

 border of the ice barrier, is but little above 32° ; and at small depths below the sur- 

 face, according to the recent observations of Payer and Weyprecht, it falls below 32°. 

 Making allowance for the known influence of pressure upon the thermometers with 

 which temperature-observations at great depths have been made in these regions, 

 there is every reason to believe that — save in cases in which the temperature of the 

 upper stratum may be modified by local causes — there is a progressive descent from 

 32° to 29°, or even lower ; so that the average temperature of the entire column of 

 Polar water may be considered to be not above 30°. 



2. In lower latitudes, the Temperature of the surface of the sea is greatly influenced 

 by solar radiation ; but the superlieating thus produced does not generally extend in 

 a marked degree much below 100 fathoms. Beneath this, in the Atlantic, is a 

 stratum of which the temperature may be said to rnnge from about 52° to 45°, in 

 all but the highest latitudes ; but the depth of this stratum varies considerably, 

 extending downwards to about 500 fathoms near the Faroe Banks, to about 700 

 fathoms oif the coast of Portugal, and to 1,000 or 1,200 fathoms nearer the Equator. 



3. Beneath this stratum is a " stratum of intermixture " in which the thermometer 

 falls rapidly, sometimes as much as 10° in 200 fathoms; and below this the tempera- 

 ture again becomes more uniform, sinking very gradually from 39° or 38', to 36° or 

 35°, at depths of 2,000 fathoms or more, near tlie Eastern border of the North 

 Atlantic. It is probable that Temperatures yet lower than these will be found to 

 prevail over the deep bottom of the Mid-Atlantic ; the recent Temperature-soundings 

 of Captain Chimmo in the Eastern Seas, made with ■ protected' Thermometers, having 

 now fully demonstrated that, even under the Equator, the bottom-temperature at 

 great depths nf the Ocean may be as low as 32°. 



4. Thus the Intertropical column may be considered as consisting of (1) a super- 

 heated stratum, of which the temperature ranges from 84° at the surface to 52° at 



1 Extracted from The English Mechanic and World of Science, tor September 20-27, 1872, 

 with additions and corrections by the Author. 



VOL. IX. — NO. CII. 35 



