I9I4-] 



ATMOSPHERIC PRESSURE. 



59 



straight and fairly tight, by the elasticity of the brass strip prongs 

 aa', aided by the tension-screws gg'^. Current is steadily supplied 

 to the test-wire through slip-rings cc' , on which rest stationary cop- 

 per gauze brushes of square cross-section 0.64 cm. (^4 inch) on each 



f- 



Fig, I. Details of Rotatable Fork 

 Supporting the Test Wire. 



Fig. 2. Details of Fork. 

 Dimensions in Centimeters. 



edge. The details of the fork dimensions are shown in Fig. 2, At 

 two points along the test-wire 32 cm. apart, pressure wires are 

 soldered to the test-wire. These pressure wires are of platinum, of 

 the same size as the test-wire. They connect with insulated copper 

 wires fastened to the sides of the fork, and terminate in the slip- 

 rings dd' carried by the motor shaft, on which rest two pairs of 



