136 



SCIENCE. 



[N. S. Vol. XVII. No. 421. 



attic floor, is a large room for arc-lamp 

 photometry. The hydraulic laboratory 

 extends through the second and attic 

 stories, giving a maximum height of over 

 25 feet. It will be used for testing gas 

 and water meters, pressure gauges, ane- 

 mometers, steam indicator springs, etc. 

 Provision has been made for a mercury 

 column in the elevator shaft, so that it 

 can be observed from the elevator plat- 

 form. 



Fresh air taken into the building through 

 an open window on the north side of the 

 second floor (adjacent to one of the photo- 

 metric rooms) passed up to the filters 

 above, then down the air shaft to the heat- 

 ing and cooling coils of the basement, and 

 thence to the blowers. 



THE PHYSICAL LABOKATORY. 



The physical building, like the mechan- 

 ical building, will be built of dark red 

 brick and Indiana limestone, the first story 

 being entirely of atone and the upper 

 stories trimmed with stone. The building 

 is 172 feet long, 55 feet wide, and four 

 stories high, besides a spacious attic story. 

 It faces the south, overlooking the city of 

 Washington. 



The corridor extends the entire length 

 of the first floor, and the exterior of the 

 building is so designed that if, in the fu- 

 ture, additional buildings should be needed, 

 they may be placed one on the east and the 

 other on the west of this building, and con- 

 nected to it by an arcade opening into the 

 corridor of the flrst floor. A basement is 

 excavated only under the central portion 

 of the building, and under the corridor, 

 the four large rooms at either end of the 

 ground floor have concrete floors upon 

 which piers may be built as they are 

 found necessary. In one of the basement 

 rooms a storage battery will be installed; 

 the others will be used as constant- tempera- 



ture rooms for experimental purposes 

 whenever they are needed. Room 4 is a 

 constant temperature room, which will 

 contain the standards of the bureau, and 

 Rooms 13 and 17 are constant-temperature 

 rooms for experimental purposes. All of 

 the rooms of this floor and the floor above, 

 however, will be practically constant-tem- 

 perature rooms. For with automatic tem- 

 perature control the temperature can be 

 maintained as nearly constant in these 

 rooms (which have heavy walls and tight 

 double windows) as it could be in any in- 

 side or underground room where an ob- 

 server is working. For the presence of the 

 observer and the heat due to artificial light 

 will disturb the otherwise constant temper- 

 ature as much or more than the fluetua- 

 ; tions in temperature of a room having 

 automatic temperature control. For those 

 cases where a machine or a piece of ap- 

 paratus is operated without the presence 

 of an observer, as for example a dividing 

 engine, an underground or inside room is 

 better, and several of these have been pro- 

 vided. 



A massive-walled, dark, unventilated 

 constant-temperature room is sure to be 

 damp, and is a very poor place for experi- 

 mental work; there are no such rooms in 

 this building. All of the so-called con- 

 stant temperature rooms are provided with 

 forced ventilation, although the ventilating 

 air current can be cut off when desired. 

 Between Rooms 1 and 2, next to the 

 outer wall, is a vertical shaft three feet 

 square, extending from the basement to 

 the attic, and in corresponding positions 

 are three similar shafts in the other three 

 quarters of the building. All the pipes 

 for distributing gas, compressed air, and 

 vacuum, hot and cold water, ice water, 

 distilled water, cold brine, and all the 

 electric wiring for lighting and experimen- 

 tal purposes are carried iip through these 



