116 R. MALLET ON THE TEMPERATURE OF THE 



tion of water upon our globe ice may have formed in polar seas, 

 while the equatorial ocean was too hot to permit the existence of 

 living organisms. At the same time the conditions of temperature 

 and refrigeration of an ocean so highly heated must have caused 

 oceanic currents of a volume and velocity, and hence of a transport- 

 ing power for solids, unparalleled in the present condition of our 

 earth. The great difference in temperature between the polar and 

 equatorial regions must have resulted also in torrential rains such as 

 are now unknown. 



Taking all these points into consideration, we may regard it as 

 highly probable that at about the epoch when the ocean-bed was 

 filled to nearly its existing level, the breaking up of solid rock- 

 matter then forming the surface of the globe, and its reduction into 

 a detrital state, must have proceeded at a far greater rate than at 

 any anterior or subsequent period of the history of our planet; 

 whilst from the known solvent power of water at high tempera- 

 tures, and from the tendency that heat and water alone, when left at 

 rest, possess to recompact and unite detrital matter into rocky 

 masses, we may likewise assume that this was also a period of 

 energetic rock-formation. If we consider the enormous masses of 

 detritus which we now find everywhere recompacted into rock, we 

 must admit that the conditions of rain, river, and littoral erosion 

 and transport, as we now witness them, will not account for these 

 evidences of ancient action, however much we may extend the limit 

 of time within which they may have acted. 



M. Daubree has observed the formation of various crystallized 

 minerals in the cavities and fissures of ancient brickwork, by depo- 

 sition from the warm waters of certain springs in the course of the 

 last 2000 years. The numerous and important observations recorded, 

 chiefly by Cotta, upon the disposition and constitution of the mineral 

 matters now found filling fissures and veins penetrating the earth's 

 crust, seem to indicate that these were originally empty, or fiUed 

 with molten matter from greater depths below the surface. In either 

 case they seem at first to have been dry, though now filled with 

 mineral matters, generally crystallized, often deposited symmetrically 

 on both sides of the central line of the fissure. The characteristic 

 mineral contents of many veins also alter completely with depth. 

 Hence it seems not improbable that these and other phenomena pre- 

 sented by the contents of fissures and veins may be due to their 

 having become charged with water from the gradually filling ocean- 

 basin at a temperature far exceeding the present boiling-point 

 of 212° Fahr., and containing abundance of mineral matters in 

 solution. 



To recajJitulate in brief the chief points of the preceding paper. 

 At some remote epoch our globe, highly heated, was devoid of liquid 

 water, all the water belonging to it being suspended as vapour above 

 its surface ; and in this state of things the boiling-point of water 

 must have been that due to the barometric pressure of the great 

 volume of water-vapour which formed the immensely greater por- 

 tion of our earth's atmosphere. Secular cooling, however, continued 



