The Department published, in the Museum Geological Series, an 

 important paper on Measurements of the Age of the Solar System, by 

 Dr. Robley D. Evans, of the Massachusetts Institute of Technology. 

 This paper, based on studies of meteorite material provided by this 

 Museum, shows that the atoms in other parts of the solar system are 

 of the same age as those composing the earth. It was already known 

 that some of the minerals of the oldest known terrestrial rocks crys- 

 tallized about two billion years ago, although the atoms composing 

 crystals are much older. This paper also suggests a probability 

 that the material substance of the universe has an age definitely 

 less than six billion years. 



Installations and Rearrangements — Geology . . . 



The Department staff has been so greatly depleted by the 

 demands of the war that it has been necessary to confine continuance 

 of work on important revisions of the exhibits, detailed in the 1942 

 Report, to the vertebrate paleontology collection in Hall 38, where 

 reinstallation continued at nearly the normal rate. 



Newly developed techniques in mounting fossil skeletons, com- 

 bined with better knowledge of skeletal posture, have made it 

 desirable to remount a number of specimens that had been exhibited 

 for several years. Nine skeletons were thus improved during 1943. 



The program of reinstallation interfered with the planning and 

 construction of cases, although one new exhibit was completed. 

 This shows the relationships of the various carnivores of the western 

 hemisphere. The history of each family, illustrated by skulls and 

 jaws, is traced back through 55,000,000 years of evolution to the 

 common ancestral group. The divergent phylogenetic lines are 

 indicated by a diagrammatic tree. 



Much life, color, and interest have been added to a number 

 of exhibits by excellent oil paintings, the work of Mr. John Conrad 

 Hansen. These carefully made pictures depict the various fossil 

 animals in their life form and in what was their most probable 

 habitat. 



A critical study of the economic and physical geology reserve and 

 study collections stored on the third floor was undertaken primarily 

 to facilitate the reinstallation of the exhibits illustrating these sub- 

 jects when this work is resumed. Although these specimens were 

 already in such good order that any specimens could be easily found 

 when wanted, it became apparent that some minor changes in 

 arrangement, some additional data on the labels, and the preparation 



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