EDWARDS. — NOTES ON PLATINUM THERMOMETRY. 555 



The subsidiary wiring for the galvanometer and battery circuits around 

 the bridge consists of ordinary " flexible cord " drawn into soft rubber 

 tubing. 



In the upper left-hand corner of the plan the coils S of accurately 

 known resistance, but approximately 5, 10, and 20 ohms in value, are 

 indicated. These are connected to give roughly the resistance of T, and 

 the desired difference is obtained from the wire readings. 



The second wire, shown between mercury cups 3 and 4, is used for 

 calibrating the standard wire, and for bringing the readings of P to con- 

 venient portions of the scale. 



The entire bridge is kept under cover and operated from the outside 

 by cords and simple levers, so far as the actual readings on the bridge 

 wire are concerned. 



Jefferson Physical Laboratory, 



Harvard University, 



Cambridge, Mass. 



