20 ORGANIZATION AND BUILDINGS. 



16-inch exhaust main in the attic, from which 4 and 6 inch branches 

 are carried down to the hoods on the first and second floors. The 

 motors are operated from the main switchboard by means of solenoil- 

 controlled switches and self-starting rheostats. 



The exhausters will maintain a velocity of 1,800 feet per minute 

 through the mains and will allow a complete change of air every 

 minute in all the hoods. 1 



Starting from the power house all the main distribution of the 

 building is through a subway which is in the form of the letter T, 

 the portion entering from the power house joining that from the 

 main building at about the middle. The diameters of the piping 

 leading to the various laboratory rooms have been calculated so as 

 to give as equal a supply as possible of gas, water, vacuum, air 

 pressure, and steam in the various rooms. In order to effect this, 

 the water and gas mains form loops on each floor of the two wings 

 of the main building, thus supplying a perfectly even circulation, 

 and the taps to the individual rooms and desks are taken from these 

 loops. The electric-light wires as well as those of the storage bat- 

 tery and telephones are carried throughout in steel conduit and 

 distributed wherever needed, so that each desk is supplied with 

 light and electric power, provided the motors to be used do not 

 exceed one-sixteenth horsepower. Where greater power than this is 

 necessary, separate lines have been run into the building. The 

 storage-battery current is supplied only to those rooms where pre- 

 sumably it will be necessary ; for example, those for mineral analy- 

 sis, physics, and weights and measures, the spectrum analysis room, 

 and the private laboratory of the Superintendent of Government 

 Laboratories. 



THE DESK ARRANGEMENTS IN THE INDIVIDUAL 



ROOMS. 



The general plan and assignment of the rooms has been men- 

 tioned above, so that only a description of the individual arrange- 

 ments is necessary. As these vary but little throughout the 

 biological and chemical wings, a description of one room for each 

 section will, with few exceptions, do for the others. In the 

 biological wing a microscope table 32 inches above the floor and 30 

 inches wide is provided along the entire available window front. 



1 PI. XII is a photograph of the engine rooms. 



