600 



Dr. W. B. Carpenter on the [June 13, 



that this heat, being wholly taken up by the Water of the Ocean, is trans- 

 ferred by its currents towards the Polar regions ; whilst of the heat which 

 falls upon the Land, a very large proportion is lost by radiation, passing 

 off into the stellar spaces. "It is in the Equatorial regions," he says, 

 " that the earth loses as well as gains the greater part of its heat ; so 

 " that, of all places, here ought to be placed the substance best adapted 

 " for preventing the dissipation of the earth's heat into space, in order 

 " to raise the general temperature of the earth. Water, of all substances 

 " in nature, seems to possess this quality to the greatest extent? and, besides, 

 " it is a fluid, and therefore adapted by means of currents to carry the heat 

 " which it receives from the sun to every region of the globe Now in 

 this assumption two facts are entirely ignored: — -first, the very small 

 depth to which the superheating influence of direct insolation penetrates, 

 as is shown in the temperature-soundings taken during my two Mediterra- 

 nean cruises (see § 67); and second, the conversion of avast amount of 

 the solar heat which falls upon the Ocean into the elastic force of vapour, 

 its surface-temperature being kept down to a tolerably regular maximum 

 by evaporation, just as the surface-temperature of the Human body is kept 

 down to a uniform maximum by its insensible perspiration. The maxi- 

 mum surface-temperature ever observed in the open Ocean is never (so far 

 as I have been able to ascertain) above 86°, the ordinary maximum being 

 about 82° ; and any higher temperature seems only to show itself in the 

 near neighbourhood of land, — as along the Guinea Coast, and in the Red 

 Sea, where a temperature of 90° is said to have been noted. Yet the 

 direct heat of radiation, measured by a thermometer with a blackened 

 bulb, laid upon a black surface, has been seen at Aden (as I am in- 

 formed by Col. Playfair) to raise the mercury to 215°. The enormous 

 amount of heat thus converted into the elastic force of vapour must 

 be carried into the upper regions of the atmosphere ; and whether that 

 vapour be there condensed into the heavy rain which falls in the region 

 of equatorial calms, or be transported by atmospheric currents to some 

 remote region, there to undergo condensation, the heat thus lost by 

 evaporation from the sea must be far greater than that lost by radiation 

 from the land. 



103. In the third place, Mr. Croll leaves almost entirely out of the 

 question the N.E. transportation of an enormous amount of heat from the 

 general surface of the Atlantic by the agency of the Aqueous Vapour thus 

 raised ; although the importance of this agency has been insisted on by the 

 most eminent authorities in Meteorology. "Thus," says Sir John Her- 

 schel (Meteorology), " aqueous vapour becomes an agent in the transfer 

 " of heat, in its latent state, from one part of the globe or from one region 

 " of the atmosphere to another." And Sir Charles Lyell, after citing 

 this passage, continues : — " The upper trade-winds (or Anti-trades), which 



* "On Ocean-currents in relation to the Distribution of Heat over the Globe," in 

 Philosophical Magazine, Feb. 1870, p. 86. 



