NO. 6 SMITHSONIAN EXPLORATIONS, I92O I3 



many unique types not represented at all in Washington. Permission 

 to prepare casts of these and thus advance our study series toward 

 the completeness which the National collections should attain, was 

 generously granted by Dr. Stuart Weller, Director of the Walker 

 Museum. In two weeks time Dr. Bassler was enabled to finish cast- 

 ing all of the Ordovician and Silurian types, leaving the remaining 

 Paleozoic species for a future trip. The work was done quickly by 

 using the modeling compound (plastocene) to make the mold from 

 which the cast is prepared. After dusting the fossil with talcum 

 powder the modeling compound is carefully pressed upon it and then 

 withdrawn, thus securing a clear-cut impression into which the plaster 

 is poured. Bubbles can be avoided by first pouring thin plaster of 

 Paris into the mold and distributing it uniformly with a camel's hair 

 brush. The thicker plaster is then introduced as usual to fill the 

 cavity. When dry the modeling compound is torn away, thus leaving 

 the complete cast but also, unfortunately, destroying the mold. 



Field-work in vertebrate paleontology was limited to a short trip 

 made by Mr. J. W. Gidley, Assistant Curator, in the latter part of 

 August to Williamsburg, Virginia, where scattered remains of a 

 fossil whale had been found in the Miocene strata outcropping nearby. 

 It was at first hoped that an entire skeleton could be secured here, but 

 careful search proved the bones to be so scattered and fragmentary 

 that no exhibition material was available although some interesting 

 additions to the collection of fossil vertebrates and some excellent 

 jMiocene shells for the exhibition series were obtained. 



Mr. William F. Foshag, of the Division of Mineralogy, at his own 

 expense made sundry trips into interesting mineral localities in Cali- 

 fornia and secured a considerable quantity of desirable material for 

 the Museum's collections, including an excellent series of borax 

 minerals. 



FIELD-WORK IN ASTROPHYSICS 

 In astrophysical research the Institution was unusually active. 

 Early in 1920, Dr. Abbot had a long discussion and correspondence 

 with Professor Alarvin, Chief of the United States Weather Bureau, 

 on the applications of solar radiation measurements to meteorology 

 now being officially practised in Argentina and Brazil on a basis of 

 daily telegraphic reports from the Smithsonian observatory near 

 Calama, Chile. Professor Marvin felt strongly the inadequacy of 

 existing solar radiation observations as a basis for studies of the 

 dependence of temperature on the solar variation. While the Chilean 

 results might be excellent, still they were for the most part not 



