TllANSACTlONS OF THE SECTIONS. 39 



The Hue witliout declination passes very near Singapore. 



In the Gulf of Bengal the ec^uator passes through the north of Ceylon (the exact 

 position "will be given). 



The position of Ligor has been corrected. It is en'oneously placed on the maps, 

 latitude 8° 24' 30". 



On the Magnetizing Function of Iron, Nickel, and Cobalt, 

 By H. A. EovTLAND. 



On Magnetic Distribution. By H. A. Rowland, 



On the Effect of Stress on the Magnetism of Soft Iron, 

 By Sir W. Thomson, F.B.S., F.B.S.K 



Meteoeologx. 



On the Influence of the Physical Properties of Water on Climate. By Henry 

 Hennessy, F.B.S., Professor of Aj^plied Mathematics in the Boyal College 

 of Science for Ireland. 



The conditions of climate depend essentially on the thermal properties of the 

 materials of the earth's outer coating. These materials are solid, liquid, and gaseous ; 

 and inaccurate ideas as to the relative thermal influence of these several substances 

 necessarily lead to erroneous conclusions regarding problems of climate aii'ecting 

 both the present meteorology of the globe and its past geological history. 



Several years since Sir John Herschel enunciated his views on this question very 

 clearly in the following words : — " The effect of land imder sunshine is to throw 

 heat into the general atmosphere and to distribute it by the carrying-power of the 

 air over the whole earth. 



"Water is much less effective in this respect, the heat penetrating its depths and 

 being there absorbed, so that the surface never acquires a very elevated temperature, 

 even imder the equator "*. These views, owing to the high name of their author, 

 have naturally commanded much attention, and have been quoted in support of 

 theories of terrestrial climate. This has been done especially by the late Sir Charles 

 Lyell, in all the recent editions of his celebrated ' Principles of Geology.' As Sir 

 John Herschel's views may still exercise an important indii-ect influence over in- 

 quiries into terrestrial climate, the author called attention to the entirely different 

 conclusions presented by him some time before the publication of the edition of 

 Sir John Herschel's work from which the foregoing passage is quoted. 



On carefully considering the properties of land, air, and water, with reference to 

 heat (namely, their specific heat or capacity for heat, their properties with reference 

 to conduction and convection, radiation and diathermancy), he came to the conclusion 

 that of all substances largely existing in nature, water was that most favourable to 

 the absorption and distribution of solar heat throughout the external coating of the 

 earth. 



The relative heat-storing power of substances depends upon their specific heat ; and 

 thus the results published by Pfaundler in Poggendorff's 'Annalen ' lor October 18G6, 

 p. 102, have an immediate bearing on our inquiries. He has found that the specific 

 neat of soils varies from 0-50 down to0*19, taking the specific heat of water as unit. 

 The lowest specific heat is found in sandy soils free from vegetable earth or humus. 

 We may in general assume that dry sand, whether calcareous or siliceous, has only 

 one fifth of the specific heat of water. As we might expect, this inquirer has found 

 that small capacities for heat are favourable to great fluctuations of soil-teuiperatwre, 

 * Outlines of Astronomy, 1864, p. 230. 



