SPECULATIVE NATURE OF GEOLOGY 687 



more systematic and thorough instruction in the non-observational side of 

 geology should be given in the educational preparation of young geologists for 

 expert work ; second, that the published work of trained experts should make 

 more explicit distinction between the inferred conclusions that they reach and 

 the observed facts on which the conclusions are based. The modern theory of 

 coral reefs supplies an illustration of incomplete deduction and erroneous con- 

 clusion. 



BEARING OF RECENT CLIMATIC INVESTIGATIONS ON GEOLOGICAL THEORIES 

 BY ELLSWORTH HUNTINGTON 



(Abstract) 



Under the auspices of the Carnegie Institution of Washington the author has 

 for three years been engaged in the study of recent changes of climate in North 

 America. His investigations have been directed not only to the dry portions of 

 the United States, but to the tropical regions of southern Mexico and Yucatan, 

 thus greatly increasing the types of climate from which conclusions can be 

 drawn. A new method of investigating the climate of recent times has also 

 been employed, namely, the measurement of the rate of growth of trees. From 

 the Big Trees of California a curve has been constructed showing the fluctua- 

 tions of climate for the past 3,000 years. A study of this curve and of other 

 similar ones covering shorter periods, together with the observations made in 

 the torrid zone, suggest certain hypotheses connected with some of the most 

 important geological phenomena. One of these is the probable nature of the 

 shifting of climatic zones which occurred during the glacial period. The phe- 

 nomena of Yucatan seem to find their best explanation in connection with the 

 theory of the development of glaciers in areas of permanent high pressure. 

 More important than this is the marked agreement which seems to exist be- 

 tween climatic pulsations and changes in the number and intensity of earth- 

 quakes and volcanoes. The agreement of these phenomena, in both short and 

 long periods, seems to point to a connection throughout geological time. This 

 leads to a far-reaching theory of the connection between changes of climate, 

 telluric movements, and some unknown force, perhaps of cosmic origin. 



Discussion 



ProL W. N. Rice : I perhaps misunderstood Doctor Huntington, but he seemed 

 to me, in the introduction of his paper, to propose the problem of finding some 

 one cause of oscillations of climate which would account both for oscillations of 

 long and oscillations of short period. It seems to me probable that climatic 

 changes are the result not of one cause, but of a complex of causes, and the 

 dominant agency in oscillations of long period is very likely different from the 

 dominant agency in oscillations of short period. Doctor Huntington has shown 

 evidence which gives some degree of probability to the hypothesis of an un- 

 known cause of climatic change on the earth, whose effect in the sun is shown 

 by changes in sun spots. But there are other known agencies which must pro- 

 duce climatic change, though there may be difference of opinion as to their 

 quantitative value. Elevation of land must produce local depression of tem- 

 perature. Elevation of large areas to high altitudes must produce depression of 



