396 Field Museum of Natural History — Reports, Vol. V. 



specimens nearer the eye, but also affords room for larger specimens and 

 those that should be examined from above. The length of the cases is 

 twelve feet, except for six which measure fourteen feet. Each alcove 

 is outlined by two of these cases, one being placed on each side of a 

 window. The cases stand with one end against the wall and extend 

 toward the aisle in the center of the hall. Including the side cases, 

 each alcove is fourteen feet wide, the open space in the center being 

 four feet narrower. On the south side of the hall, the alcoves are twelve 

 feet deep. On the north side they are fourteen feet deep. In the center 

 of each alcove one or two table cases, four by six feet, are placed. Mid- 

 way of the hall, opposite the passage connecting with the next hall to 

 the north, the character of the alcoves is varied, the principal change 

 being the replacement of some of the long cases by two tall cases, four 

 feet square. These cases are glazed on all sides, except the base, and 

 contain massive specimens and materials of special character. There 

 are twenty-six alcoves in the hall as a whole and they contain forty-two 

 twelve-foot and forty-four other cases. The ores of the heavy metals 

 and the building stone collections are for the most part re-installed in 

 their original cases and in their original positions in the cases. The 

 exigencies of re-installation have compelled some changes, but they are 

 relatively few. The addition of two cases against the east wall has made 

 possible the re-display of a case and a half of ores which had been 

 withdrawn from exhibition for a number of years on account of lack of 

 space. Except for the building stones and alkalies, that part of the 

 non-metallic economic collections which appears in upright cases in this 

 hall has been transferred to cases of a different type from those formerly 

 used. This has made some re-arrangement necessary, owing to the differ- 

 ent capacities of the two types of cases, and withdrawal of some of the 

 material has been unavoidable, but for the most part the original 

 arrangement of the specimens has been retained. It was necessary to 

 spend much time and labor in cleaning the specimens of ores. The 

 method employed has been first to remove the dust by use of a vacuum 

 cleaner, then to wash and dry the specimens. As water alone or soap 

 and water was found not to attack a sooty coating which had sometimes 

 formed through exposure to a smoky atmosphere, and as the more corro- 

 sive detergents could not be used, some care in selecting a suitable cleans- 

 ing agent was found imperative. Satisfactory results were, however, 

 secured by use of cold water containing a moderate quantity of carbonate 

 of ammonia. As the collections in this hall are now arranged, there are 

 shown at the east end and extending from the east entrance about half 

 way down the hall, the ores of the precious and base metals. These are 

 arranged in the order of the installation employed in the old building; 



