272 Field Columbian Museum — Reports, Vol. II. 



tion of radioactive minerals, prepared in the Department, was also 

 installed here. This collection contains all known radioactive min- 

 eral species so far as they could be procured, and in connection 

 with each specimen is exhibited a radiograph made by the specimen 

 itself upon a photographic plate. Electrical tests of the radioactivity 

 of many of the specimens were also kindly made by Prof. R. A. Millikan 

 of the University of Chicago, giving data which are exhibited in 

 connection with the collection. The series of models of famous dia- 

 monds exhibited in the same hall has been increased by the addition 

 of seven important ones not before represented, and the whole series 

 has been reinstalled in an attractive manner. In Hall 65 an individual 

 case has been provided for the large glaciated copper boulder presented 

 by Mr. Joseph Austrian. In connection with the labeling of the syste- 

 matic rock collection in Hall 66, a careful re-identification of the speci- 

 mens has been made, and a rearrangement carried out in order to 

 improve the classification. In connection with this work, about 

 twenty sections for microscopic study were made. Several complete 

 rock analyses were also made in the Department laboratory. A num- 

 ber of photographs made by the Curator in Mexico were framed and 

 installed in the hall in connection with the series of volcanic rocks 

 collected at the same time. In Hall 77 a large framed geological 

 map of Japan has been installed, also a transparency of Mont 

 Pelee, presented by Mr. Morris K. Jesup, and four geological photo- 

 graphs loaned by the Curator. The interiors of the cases in Hall 

 7 1 have been cleaned and repainted where necessary. New meteorite 

 specimens, as fast as received, were placed on exhibition in Hall 62, 

 and frequent treatment with paraffin has been given all specimens 

 showing a tendency to decompose. About twenty sections of as 

 many stony meteorites were made for purposes of microscopic study. 

 Upon ten of the floor cases in Hall 35 large descriptive labels have been 

 placed. Throughout the paleontological collections, where the beauty 

 or delicacy of structure of a specimen was such as to make it desirable, 

 there have been installed magnifying lenses two inches in diameter 

 and of three-inch focus. About sixty lenses have been so placed, and 

 an increased interest in the study of the collection by visitors is 

 noticeable as a result. In the paleontological laboratory, a consider- 

 able amount of time was devoted to the preparation of the incomplete 

 skeleton of the huge dinosaur, Brachiosaurus, collected in 1900. The 

 remains were too few in number to be of much value for exhibition 

 purposes, but the great scientific importance of the specimen, due to 

 its being the type of a new family and genus, and the largest known 



