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sary. In a University Museum like ours, which displays only a 

 small part of its resources to the public, and where the great 

 bulk of the collection is stored in smaller rooms to be available 

 for research, such a course as that pursued by the Geological 

 Department is essential. There is a natural temptation for the 

 Instructors to make the freest possible use in their class-room of 

 the specimens originally placed on exhibition only for the benefit 

 of the public, and of the students as part of that public. It needs 

 but little experience to show that the use of the collections in- 

 tended either for exhibition or for research for purposes of instruc- 

 tion is ruinous. No specimen can be moved from its case without 

 detriment, and it seldom goes back to its place in as good a con- 

 dition as it left it. 



The Director of a Museum must decide how far it is for the 

 benefit of science to allow specimens once placed on exhibition or 

 intended for research to leave their shelves. My own experience 

 teaches that, when a collection is once placed on exhibition, no one 

 should be allowed to have access to the cases or to the special col- 

 lections to remove the specimens, and nothing should sanction 

 their use for purposes of instruction or of scientific examination 

 except in the clearest case of a positive gain for science by such a 

 course. The Director of a Museum intended to meet the demands 

 of the public, of the investigator, of the teacher, and of the student 

 must provide each with the suitable material, and all attempts 

 to perform these various functions with one collection will neces- 

 sarily fail. This principle means of course a large amount of 

 duplication, but this is essential for the safekeeping of valuable 

 collections, which are too often sacrificed for comparatively unim- 

 portant scientific indulgences. 



ALEXANDER AGASSIZ. 



Cambridge, October 1, 1894. 



