374 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1910. 



the saharas of to-day, which are even now held by this school of 

 thought to be creeping out persistently on the once fertile lands. 

 Thus is reached our own time, when heat and air and moisture are 

 all running low, j)utatively, and are thus foreshadowing the predes- 

 tined end in the not distant future. 



Life history is thus made but an episode in the midst of this great 

 declension from the too hot and the too much to the too cold and too 

 little. The life period merely spans a lapse on the slope from excess 

 lo emaciation. 



The logic of all this is plausible, the premises once granted. Start- 

 ing with the hypothetical postulates, the conclusions seem almost 

 necessarily to follow. The details, indeed, may not all have been as 

 mapped, but, the premises granted, the general course of progress 

 was scarcely less than inevitable. Sources of delay and causes of 

 deviation might, indeed, have been found in means that furnished a 

 greater or less supply of air, or water, or heat to offset the waste, but 

 the presumption of a downward trend carrying the whole along with 

 it is not easily escaped. 



In point of fact, the general conception of a progressive declension 

 dominated the geologic thought of the last century. Not only did it 

 dominate the forecasts, but it gave direction to the interpretations of 

 the geologic record, and in no small degree it unconsciously influ- 

 enced the observations of geologic phenomena, and this domination 

 continued well down to the close of the last century and is far from 

 obsolete to-day. 



But logical and plausible as is this inherited picture of the history 

 of the earth, it was hung on the particular hypothesis of the genesis 

 of the earth that was then currently accepted. However-logical, its 

 logical strength was only that of the hypothesis on which it was hung. 

 I say logical strength advisedly, for outside the logic of the concept 

 there was always the appeal to the record. This appeal was made 

 and was thought to be in the main confirmatory. The strata of high 

 latitudes were found to contain relics of life of subtropical types, and 

 this was found true not only of the very early ages, but of ages well 

 down toward recent times. Figs and magnolias grew in Greenland 

 as late as the Tertiary period. So impressive was the presence of 

 subtropical plants in strata almost under the very edge of the Green- 

 land ice cap, that it gave deep hold to the logical inferences with 

 which it seemed to be so strikingly in consonance. Phenomena not 

 so consonant with the concept were easily overlooked or lightly 

 passed by, as is our wont when too much impressed by what must be. 

 It is, however, a merit of modern science that it prompts us to put 

 to the front that which is and to relegate that which merely must 

 be to a secondary category. And so all along during the past century 

 the inconsonant elements of the record were gathered as well as the 



