MACKIE — ON DR. ERANKLAND's GLACIAL THEORY. 163 



rises ; u the atmosphere," says Dr. IVankland, " is the true condenser, 

 for the aqueous vapour that rises in it to its utmost heights radiates 

 its heat into space ; the mountains are the receivers of the rain and 

 snow precipitated." So far we have no objection to the doctrine. 

 But to apply it practically to the production of the phenomena of 

 the " Glacial period," which everybody knows was a geological period 

 of intense cold, almost immediately preceding our own historical age, 

 and possibly, according to recent ideas, absolutely including the early 

 portion of the human era. Before this, according to the general 

 tenor of geological notions, the earth had from the beginning of time 

 possessed a gradually diminishing but still always higher temperature 

 than it does at present; but whether this doctrine is not, upon 

 stratigraphical evidences, open to grave doubts, we are by no means 

 sure. Admitting this, for the sake of the argument, we have to see 

 how Dr. Erankland applies Professor Tyndall's radiant-heat principles 

 to the production of a period of intense cold. 



The points which he deemed his theory must meet are thus stated. 

 The glacial phenomena must extend over the whole globe ; their oc- 

 currence must be of geologically recent date ; they must have been 

 preceded by ages during which glacial action was wanting ; and they 

 must be followed by a time during which there was a re-tendency 

 towards an ameliorated condition of temperature. Moreover, Dr. 

 Frankland considers it essential to show that during their con- 

 tinuance atmospheric precipitation was greater, and the snow-line 

 lower, than at present. All these conditions, Dr. Frankland asserts, 

 would naturally result from the gradual cooling of our planet ; so 

 that, according to his view now put forth, " the sole cause, of the phe- 

 nomena of the Glacial epoch" — or period of universal intense cold 

 all over the earth — " was a former higher temperature of the ocean 

 than that which obtains at present." Admitting that our globe was 

 once so hot that all the water now in it was then in nuhibus and not 

 in the ocean cavities at all, he goes on to its first condensation into 

 liquid, and then from the cessation of the boiling of the seas through 

 a gradual diminution of temperature down to their actual state ; a 

 corresponding refrigeration of the land being contemporaneous. It 

 was, he says, during the later stages of this cooling operation that 

 the Glacial epoch occurred. For this result, however, he is con- 

 strained to the assumption that the earth and the sea-water have 

 cooled at different rates. To prove this he brought forward experi- 

 ments upon the differences of cooling between a cube of granite and 



