August 29, 1902.] 



SCIENCE. 



331 



discriminating have been regarded as lead- 

 ing geologists. And in one or two cases these 

 men have gained a wide hearing. But the 

 systems which they built up had little or no 

 relation to the world ; and they disappeared 

 with the death of their authors. But a 

 geologist must not only do systematic field 

 work at the outset; he must continue to do 

 such work through the years to a ripened 

 age. Not infrequently a geologist, who in 

 early life has done systematic field work, 

 drops this work and continues writing geo- 

 logical philosophy; but this is a precarious 

 course, which sooner or later makes of him 

 what one of our members calls a ' closet geol- 

 ogist. ' It is only by never-ending action 

 and reaction between the complex phenom- 

 -ena of geology in the field and reflection as 

 to the meaning of the phenomena that sure 

 results can be obtained. 



While one should spend a part of each 

 year in the field, I suspect that many more 

 discoveries of geological principles are 

 made in the office or in the laboratory than 

 in the field. The cow collects the grass in 

 the meadow, and afterwards lies down to 

 chew the cud and digest the food. So the 

 geologist in the field, in the midst of in- 

 numerable facts, collects all he can. His 

 notes are a record of his daily collections; 

 and if a successful geologist, of his daily im- 

 perfect inferences and deductions. But 

 during the eight or nine months of office 

 and laboratory work he has full opportunity 

 for reflection. He is then likely to see more 

 of the common factors of the facts col- 

 lected ; is more likely to see deeper into the 

 underlying principles which explain them. 



This is still more true of the facts collect- 

 ed in the current and during the previous 

 years. Indeed, in the field the observations 

 of the current year are often too prominent 

 on account of their recency, and it is only 

 after some months have elapsed that they 

 take their triie proportion in connection 

 with observations of previous years. The 



use of the material collected not in one year 

 only, but through many years, is necessarily 

 done in the office or in the laboratory, and 

 it is only from such large masses of material 

 that broad generalizations can be made. 



But the inductions and deductions made 

 in the office and the laboratory during the 

 winter should be tested in the field in the 

 following year in the light of the new ideas. 

 The new ideas should not by a fraction 

 modify the correctness of the observations 

 of the previous years ; they should be found 

 as accurate as when made. But observa- 

 tions are always incomplete, and with a 

 new idea one invariably adds valuable ob- 

 servations which were not noted before the 

 idea was available. 



I once wrote to a number of the geologists 

 of this and other countries, asking the direc- 

 tions and dips of the dominant cleavages and 

 joints for the various districts and regions 

 of the world with which they were familiar. 

 From only a single geologist did I obtain 

 data of value. Some geologists wrote that 

 they had not time to observe such subordin- 

 ate phenomena! These men had evi- 

 dently not learned the principle that the 

 small but numerous agent or force or struc- 

 ture may have as great or greater impor- 

 tance than more conspicuous but less com- 

 mon ones. Darwin should have taught 

 every scientist the principle of the quanti- 

 tative importance of the small factor when 

 he showed how great is the work of the 

 apparently insignificant earthworm. It 

 seems to me that joints are one of the im- 

 portant phenomena of geology; and this is 

 true whether the point of view be defor- 

 mation alone, physiography, metamorphism, 

 circulation of groundwater, or the genesis 

 of ores. 



While tiie work of each geologist should 

 be based upon thorough field and office 

 work, and thus have an inductive basis, one 

 should not there stop, but should by deduc- 

 tion ever be looking forward. No one ever 



