MEMOIR OF RALPH STOCKMAN TARR 37 



Tarr's field-work was done at widely separated points on the North 

 American continent. He worked in Massachusetts on the geology of 

 Cape Ann ; he helped to unravel the structure of the Gay Head cliffs on 

 the island of Marthas Vineyard — a locality made classic by the earlier 

 labors of Edward Hitchcock and Sir Charles Lyell ; he made glacial maps 

 of parts of that State and Connecticut, as well as of New York; he car- 

 ried his studies of glacial erosion on at Mount Katahdin, Maine, and in 

 the Finger Lake region ; he did areal work in Texas and the highlands of 

 New Jersey, and made geological and physiographic observations in 

 New Mexico and Montana, on the Bermuda Islands and in Cape Breton, 

 and finally he left his name indelibly associated with the pioneers of the 

 scientific exploration of Greenland and Alaska. 



It was not his privilege to devote his life to the painstaking decipher- 

 ment of the geological structure and form of a single natural province 

 of the continent. The sporadic character of his early work, both as to 

 locality and subject-matter, was under the control of the inexorable law 

 of necessity, tempered by favoring opportunity. Tarr came into geology 

 at the time of the birth of the daughter science of physiography. As a 

 student of Davis, it was natural that he should enter the new field. If 

 the orthodox geologist at times complains of the numerous breaks in the 

 ranks of the old school on the part of those who have been trained in its 

 methods only to betake themselves to the once despised superficial geol- 

 ogy, it must now be borne in mind that a knowledge of existing cause- 

 is the key to the past, that the study of peneplains has thrown most im- 

 portant light on unconformities, and that the study of glacial deposits 

 has elucidated the nature of tillite and led to the recognition of the fal- 

 sity of the doctrine of a globe gradually declining in temperature from 

 Cambrian times to our own. Tarr's varied training in zoology ; geology, 

 petrography, and physiography gave him a broad insight into the prob- 

 lems of the new field of research. 



Of his contributions to geology proper we have the phenomenon o\' rift 

 in granite, which appears to be new to the science. Mis descriptions o( 

 the dislocation which gave rise to the Alaskan earthquake of L899 is a 

 most important addition to our knowledge of the relation o( earthquakes 

 and faults, with accompanying changes of level of the hmd in relation 

 to the sea. His recognition of earthquake shocks ns ;i factor in glacial 

 motion is an important and helpful contribution to our knowledge o( the 

 causes which affect the mysterious advances and recessions ^\' glaciers, 

 one which promises, when fully elaborated, to throw yet further lighl on 

 the physics of the globe: His studies of glacial erosion in the regions o( 

 acting and vanished glaciers include such discoveries as the hanging 



