ELISHA MITCHELL SCIENTIFIC SOCIETY. 11 



especially the case in connection with the topographical work of 

 the survey. There was in 1866 no even approximately accurate 

 map of the western part of the State u})()n which could be laid 

 down the data for a geological map. During almost the entire 

 period of the existence of the survey Professor Kerr, in making 

 his geological excursions, combined topographical and geological 

 work. And in this way he became quite proficient in the detec- 

 tion of geological structure as exhibited in the topography of 

 the region. 



In some cases his topographic observations were only approxi- 

 mate, taken with a pocket compass, pocket level, or aneroid 

 barometer; but as a rule these instruments were used only to 

 fill in details after the more important measurements had been 

 taken by means of more accurate instruments. During several 

 seasons, early in his connection with the survey, Professor Kerr 

 devoted a considerable portion of his time to topographic 

 work (or geological and topographical work combined) in the 

 mountain region. 



These numerous topographic observations, made by himself 

 and his assistants, bore fruit in 1882, when he published the new 

 State Map, to be used as a base for the geological map. 



In connection with this work, he examined all the accessible 

 records of the surveys of railroads, rivers, canals. State and 

 county boundary lines, and of the United States Coast and 

 Geodetic Survey, within the limits of the State; and com- 

 binino; the results of these examinations w^th those of his own 

 and his assistants' work in the field, he produced a map which 

 in point of accuracy is incomparably in advance of any map of 

 the State that preceded it; and maps published subsequent to its 

 date will be indebted to it more than they are wont to admit. 

 Its preparation cost its author no small part of fifteen years of 

 labor. 



Professor Kerr was a rapid worker in the field, and at no time 

 could this fact be observed to better advantage than during one 

 of his horseback trips through the mountain region of the State, 

 which he seemed to enjoy so much. After his appointment as 



