66 



ordinary conditions, 4 square feet to the horse power, and under extreme con- 

 ditions, but 2 square feet. • 



The draft in a stationary plant having a chimney 50 feet high is less than 

 0.5 of an inch of water. The locomotive frequently runs under a draft as heavy 

 as six inches, making it necessary for the tireman to keep a very thick fire on the 

 grates. 



With such great differences existing between the conditions apparently re- 

 quired by economy and those actually found in locomotive practice, it would be 

 expected that the evaporative efficiency of the latter would be small by compari- 

 son. It is interesting to note, however, that in spite of the disadvantages under 

 which the locomotive labors, its evaporation is seldom less than 50^ of the best 

 evaporation given by stationary plants. 



The Influence op Heat, the Electric Current and Magnetism Upon 

 Young's Modulus. Mary Chilton Noyes. 



A series of experiments were carried out in the physical laboratory of West- 

 ern Reserve University to determine the effects of heat, of an electric current and 

 of magnetism upon the elasticity of piano wire, and of copper and silver wire. 

 The wires were heated by means of an electric current from a storage battery, 

 the current sometimes going throngh a magnetizing helix surrounding the wires, 

 sometimes through a non-inductive coil, and sometimes through the wires them- 

 selves. The methods of heating were used in different order with different pieces 

 of wire, in order to detect, if possible, any temporary or permanent effect which 

 was not due to the heat, but no such effect could be found. 



Tiie thermal co-efficient of elasticity for the piano wire was found to be 4.69^ 

 for 100°. For the silver wire it was about 8% and for the two specimens of cop- 

 per wire tested 13% and 7%. The permanent change in elasticity produced by 

 repeatedly heating the wires was from one to two per cent. 



With the silver and copper wires the effect of heat upon the elastic limit was 

 determined. The limit was found to decrease quite rapidly and regularly as the 

 temperature was raised. The two specimens of copper wire tested were found to 

 give quite different results for the thermal co-efficient of elasticity, the co-efficient 

 of expansion and the co-efficient of decrease in the elastic limit with rise of 

 temperature. 



