ANNIVERSARY ADDRESS OF THE PRESIDENT. IxV 



4. Hygrometric condition of atmosphere, cloud-formation, and 



rainfall. 



5. The currents of the air and sea. 

 (3. The internal heat of the globe. 



The effect of the latter, being at present valued at only r^° C, 

 may be neglected in questions relating to recent periods, although 

 it must, in all probability, have formed an important item at the 

 time of the more remote geological events. 



The decrease of temperature for a given amount of elevation in 

 the air is so distinctly dependent on the latitude of the place (being 

 more in the polar and less in the equatorial regions), that a formula 

 may be established by the aid of which the mean temperature for 

 any required elevation, under a certain latitude, may be approxi- 

 mately calculated. But it is requisite for this purpose to know the 

 mean annual temperature of some neighbouring locality of measured 

 height above the sea ; and thus a comparison of the observed con- 

 ditions of sea-climate and land-climate respectively has to be insti- 

 tuted, from which it comes out, among other deductions, that in the 

 latitude of 33° 24' in our northern hemisphere the mean annual 

 temperature of a totally marine and of a continental climate would 

 be the same, whilst northward of this parallel the mean tempera- 

 ture of the land-climate would be colder, and southward would be 

 warmer, than that of the oceanic climate. And the ultimate con- 

 clusion is, that although the unsymmetrical distribution of land and 

 sea on the earth's surface must exercise an undoubted influence on 

 the advance and retrocession of the glaciers, it is not adequate to 

 account for the glaciers of the Diluvial period. 



The relation of an oceanic climate to glaciers has lately received valu- 

 able illustrations from the writings of Drs. Haast and Hochstetter, 

 on the Southern " Alps " of New Zealand. Their chief results are 

 given in the last chapter of the sumptuously printed and illustrated 

 volume which has recently been published by the latter geologist *. 



Here, in the latitude of 43° to 44° S., whilst the average lower ter- 

 mini of the glaciers on the east side of the ridge are much higher, the 

 great Tasman glacier descends to 2774 feet above the sea-level ; but 

 on the western side of the ridge the Prancis Joseph glacier, although 

 of much smaller volume, reaches no less than 2000 feet lower, or to 

 a height of but 705 above the sea. This strange contrast is accom- 

 panied by the notably heavier precipitation, and the frequent cloud 

 and mist of the western coast. And as the large development of the 

 glaciers, generally, in this region seems attributable to the equable 

 and humid oceanic climate, so the exceptional advancement of the 

 foot of the Francis Joseph glacier among the vegetation of the low- 

 lands is to be explained, not by a low mean annual temperature, but 

 by a peculiarly low temperature of the summer f. 



* New Zealand, its physical geography, geology, &c., by Dr. Ferdinand von 

 Hochstetter. Stuttgart : J. G. Cotta. 1867. 



t The mean annual temperature of Christchurch was 53|° in 1864, that of 

 the summer 61^°, and of the winter 44^°. It is believed that the annual average 

 on the west coast is very similar. 



