39* Field Museum or Natural Histoby — Rcforts, Vol. V. 



gpedmens nearer the eye, but also afiords room for larger spedmens and 

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

 twelve feet, cxccjH 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 ca.scs, 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 rc^ilaccment of some of the long cases by two tall cases, four 

 feet square. These cases arc 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-foxir 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 rc-in.stallation have compelled .some changes, but they are 

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

 pojwiblc the rc-display of a case and a half of ores which had been 

 withtlrawn from exhibition for a number of years on account of lade 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 tran.sfcrred to ca.scs of a different tN-pc from those formerly 

 u.scd. This has made some re-arrangement neccs.sary, owing to the differ- 

 ent capacities of the two t>'pes of cases, and withdrawal of some of the 

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

 arrangement of the s^^ecimcns 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 

 deaner, then to wa.sh and dr>' 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 smok>* atmosphere, and as the more corro- 

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

 ing agent was found imperative. Sati.sfactor>* results were, however, 

 secured by u.se of cold water containing a moderate quantity of carbonate 

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

 shown at the east end and extendi v' ♦''■ "a the cast entrance about half 

 way down the hall, the ores of the ; . . - -i- <i base metals. These are 

 arranged in the order of the installation <  cd in the old building ; 



