Dr. Croll's Hypotheses on Geological Climates. 229 



he thinks, is caused by the ocean-currents, which bring an 

 immense quantity of heat from low to high latitudes. That 

 ocean-currents have a great influence on the temperature of 

 our earth I do not deny, but it is not so great as Dr. Oroll 

 believes. 



To prove this, I will take two places in as different lati- 

 tudes as possible,, and both uninfluenced by the ocean-cur- 

 rents. Ths first is Iquitos, on the Amazons, 3^° S., and about 

 300 feet above the sea-level. The mean yearly temperature 

 is 76 0, 4. The reduction to sea-level would make it about 

 77°*8, and the reduction to the temperature of the equator 

 would give 78°*3. Now Iquitos is more than 1000 miles 

 from the Atlantic ; and though nearer to the Pacific, is sepa- 

 rated from it by the chain of the Andes. It must be admitted, 

 then, that this place gives us a good idea of the temperatures 

 near the equator, uninfluenced by the heat-abstracting influ- 

 ences of ocean-currents. 



The other place which I choose for comparison is Verk- 

 hojansk in N.E. Siberia, under 67° N., and having the coldest 

 winter known on our globe (January, —56° F.). I think it 

 will be readily admitted that this place is out of the influence 

 of ocean-currents, bringing heat from low latitudes, and in 

 most favourable circumstances for radiation of heat. The 

 mean yearly temperature of this place is 1°*9 F.; the reduc- 

 tion to sea-level may bring it to about 2°*3 F.* 



Thus we have, out of the influence of ocean-currents, the 

 following mean yearly temperatures at sea-level : — 



°F. 



Equator 78'3 



67° N. lat 2-3 



Difference .... 76-0 



Reasoning on the premises of Dr. Croll, we ought to expect 

 a difference of 172° F. between the equator and 67° K The 

 actual difference is less than half that amount (scarcely over § ) ; 

 yet heat is certainly not abstracted from the vicinity of the 

 equator in the interior of South America by ocean-currents, 

 nor are the continental regions of N.E. Siberia warmed by 

 ocean-currents. 



The Rev. O. Fisher f has already proved that if Dr. Croll's 

 reasoning w T as right, the mean temperature of the equator 

 should be higher in January than in July by 21° F., on 

 account of the greater nearness of the earth to the sun in the 



* The actual height is not known, but in any case small. 

 t Nature, vol. xx. p. 577. 

 Phil. Mag. S. 5. Vol. 21. No. 130. March 1886. R 



