50 American Association of Museums 



sufficiently well informed to differentiate between a museum of fossil 

 plants and an art gallery are probably very few in number and need 

 not be considered in any scheme of museum economy. Neverthe- 

 less, experience has demonstrated that certain factors in connection 

 with fossils in general require careful consideration in regard to ex- 

 planatory labeling if any display of such objects is to have its proper 

 educational value, even to the person of average information and 

 intelligence. It is not safe to assume the possession, by the general 

 public, of even the most elementary knowledge relating to natural 

 objects. 



For example, an astonishingly large number of persons are evidently 

 puzzled over the problem of how a fossil, especially such a fragile 

 object as a leaf or flower, could have become imbedded in solid rock 

 or left its imprint in such hard material. To such persons, of course, 

 some information in regard to the origin of sedimentary rocks is 

 necessary, and some explanation of the difference in origin between 

 sedimentary and igneous rocks, in order that they may not expect 

 to find fossil remains in a trap dyke as well as in the sandstone asso- 

 ciated with it, as some occasionally do in connection with the rock 

 of the Hudson River Palisades. How best to impart this information 

 by means of an explanatory chart is something that I have been 

 seriously considering. 



Probably the one question which is most frequently asked in 

 regard to a fossil is how old it is, or how long ago in the world's history 

 was the geologic period in which it lived. Disappointment is usually 

 expressed because definite figures in years can not be given. The age 

 of the world, the extent of geologic time, and the slowness of geologic 

 processes, are matters in regard to which most persons apparently 

 have no conception, and a majority are frankly incredulous when 

 tens or hundreds of thousands of years are mentioned in connection 

 with the relatively recent remains of the Quaternary Period, and 

 indefinite millions of years in connection with those which preceded it. 



It has occurred to me that possibly a chart, giving the calculations 

 which have been made of time ratios in connection with the primary 

 geologic time divisions, might be utilized in order to convey some 

 idea of this factor, in preference to any attempt to indicate definite 

 figures for the probable antiquity of the several geologic periods. 

 With this idea in view, I have prepared the following chart, adapted 

 from a similar one by Dr. Lester F. Ward: 



