-'« NIXin'EEXTH HKl'ORT. 



"No one doubted his meaning, and tlie effect was tremendous. One 

 lady fainted and had to be carried out; I, for one/' says the chronicler, 

 "jumped out of my seat." 



If the emancipation of science from coercion or restraint from witliout 

 had arrived with tlie final triumjili of the doctrine of evolution, can it be 

 truly said that theories are constructed even in this generation as the 

 result of a process of wholly untrammeled reasoning; or, on the other 

 hand, is it the fact that with the frailties inherent in human nature they 

 still embody elements of weakness which are due either to tlie deficiencies 

 in training of their authors, to prejudices or bias conditioned ujDon time 

 or place, or to some other cause .^ 



It is usually considered to be the special function of a president to 

 recount in his address in particular the great triumphs of science, and to 

 touch but lightly, if at all, upon any less encouraging aspects of his 

 science. I propose in the time that remains to me to pursue a some- 

 wliat different course, and by the use of examples selected from the field 

 of my own special studies to discuss what may jierhaps be called the 

 psj'^chology of theories and the conditions which determine their accept- 

 ance. 



To some extent it is inevitable that theories should reflect the in- 

 dividuality or the environment of tJieir authors. This is particularly 

 true in the field of natural science, where the laboratory is the world 

 itself, a portion only of which can be brought under the observation of 

 any one individual. Geological processes are different both in degree 

 and in kind according as they are studied under conditions of aridity or 

 of excessive humidity, under tropic heat or polar cold. It is unquestion- 

 able that geology having developed as a science in those temperate 

 regions of moderate humidit}- which have permitted a high degree of 

 civilization, is correspondingly defective, and must be modified if it is to 

 be universal in its scope. The physical geology of deserts has been 

 studied seriously only during the present generation. It is within the 

 last decade only that the attention of geologists has been focused upon 

 the subpolar latitudes, and the geology of the tropical jungles is yet to 

 be written. 



To indicate how the peculiar environment, the conditions of the time, 

 and the special activities of the individual have left their impress upon 

 a well-known theory, I may cite the case of Robert Mallet and his 

 centrum theory of earthquakes, a theory which received general accepta- 

 tion and was orthodox doctrine among earthquake specialists for full half 

 a century. Robert Mallet was educated as a civil engineer, and in 1831 

 became a partner with his father in the foundry industry at Dublin. 

 During the Crimean War he constructed monster mortars of thirty-six 

 inch caliber which embodied new ideas and were completed in 1854. 



