Septembee 2, 1910] 



SCIENCE 



293 



tlie large amount of special apparatus re- 

 quired in research, or the repair of the 

 even greater number of instruments broken 

 in the general laboratory courses. Three 

 machinists find themselves constantly 

 busied in this work of production and re- 

 pair. 



Two smaller, fairly well equipped shops 

 in different parts of the building are open 

 to any one using the laboratory, for the 

 rough repairs which often have to be made 

 in an emergency. 



The experimental equipment of the 

 laboratory is most generous. In addition 

 to the supply of the usual apparatus found 

 in about all laboratories, the following, 

 perhaps somewhat unusual, items of equip- 

 ment have been installed and are in suc- 

 cessful operation: 



Refrigeration and Constant-temperature 

 Rooms. — A four-ton ammonia refriger- 

 ation plant, driven by a ten-horse-power 

 motor, provides for the cooling, or refrig- 

 eration, of two constant temperature rooms. 

 These rooms, one 10 ft. X 10 ft. X 8 ft., 

 the other 10 ft. X 20 ft. X 8 ft., are insu- 

 lated by cork board of thickness sufficient 

 to cut off practically all inflow of heat. 

 On the test run these rooms were cooled 

 simultaneously to — 7° F. and +8° F., 

 respectively. By means of a specially de- 

 vised electrical thermostat, the tempera- 

 ture of the larger room has been held at 

 32° F. for twenty-four hours, with a varia- 

 tion of but one-twentieth of a degree dur- 

 ing that time. By the use of the appa- 

 ratus installed, the temperature of these 

 rooms may be kept constant at any value 

 between the lowest attainable in the room 

 and the outside atmospheric temperature, 

 the rooms being ventilated all the while. 



Electrical Standards Room. — A room has 

 been set apart and equipped for convenient 

 and rapid comparison of the various elec- 

 trical standards. Potentiometers, bridges 



and comparators are kept set up for use 

 at any instant. The primary electrical 

 standards of the laboratory are reserved 

 exclusively for use in this room. It is 

 provided also with a Callender recorder 

 which can be connected by a special signal 

 circuit to any room in the building, for 

 registration of temperature or measure- 

 ment of resistances. 



Liquid Air Plant. — In the main ma- 

 chinery room, a two and a half liter liquid 

 air plant, with Hampson liquefier and 

 Whitehead compresser, is driven by belt 

 from the motor of the main motor-genera- 

 tor set. 



Pressure and Vacuum Systems. — Two 

 systems of piping run from this main ma- 

 chinery room to all parts of the building, 

 for supplying compressed air or vacuum 

 as needed. To one system is connected an 

 automatically controlled, motor-driven 

 pressure pump, capable of producing a 

 pressure of 100 lbs. per sq. in. By mere 

 shifting of the stops on the controller, 

 any pressure between that of the atmos- 

 phere and 100 lbs. per sq. in., with a varia- 

 tion of about one unit, can be supplied at 

 any time, to any room where needed. 



To the other system of piping a vacuum 

 pump is coupled, which can produce a 

 pressure of one half millimeter of mer- 

 cury. This pump is not automatically 

 controlled but can be started at any time 

 by the throwing of a switch. By this ma- 

 chine a vacuum of the value named may 

 be obtained in three or four minutes in 

 almost any part of the laboratory. 



But the most distinctive experimental 

 feature of the laboratory is its electrical 

 equipment. This is, the writer believes, 

 unique in magnitude, and in the flexibil- 

 ity of the means of distribution of currents 

 under widely different voltages. 



Energy is received by means of 2-phase 

 alternating currents from the central 



