04 



Mr. T. G. Bedford on the Expansion of 



After the experiment of March 30, the ice and steam 

 points were re-determined, and were found to have changed 

 considerably. Accordingly, from this date, a re-determination 

 of the fixed points was made after each exposure to a high 

 temperature, and the values then obtained were used in the 

 reduction of the observations of the preceding experiment. 

 On account of the change, the observations of March 21-29 

 inclusive were not reduced. 



In making an experiment the tube was heated to as high a 

 temperature as possible, and observations of length and 

 resistance were made. By diminishing the gas-supply the 

 tube was then allowed to cool gradually, and when the 

 temperature had become steady, length and resistance mea- 

 surements were again made ; this process was repeated till 

 the tube reached the temperature of the air. The observa- 

 tions were recorded thus : — 



Table II. 



Time. 



Glass 

 tube. 



Bench. 



Porce- 

 lain tube. 



R. L. 



Coils. 



Bridge 

 wire. 



Temp, of 

 Coils. 



7.37 p.m. 





1465 



101285 



70,50 



D,H 



+ 1-5 



15-63 



7.54 „ 



10-4212 



14-65 













8.17 „ 





14-9 



10-2045 



60,40 



B, 0, E, 



+3-6 



14-9 



Columns 2 and 4 give the sum of the microscope readings 

 for the standard length and the porcelain tube respectively. 

 The porcelain tube projected from the furnace so that a 

 length of about 6 cm. at either end was not directly heated 

 thereby. The temperature of the tube in the neighbourhood 

 of the marks was taken roughly by means of mercury 

 thermometers, and is recorded in column 5. 



The results of experiments 1, 2, 7-10, are collected in 

 Table III. (p. 96) ; the results of the last four experiments are 

 represented in the diagram. 



It appears from the diagram that, from 0° to 600°, the 

 results are represented fairly well by a curve given by the 

 formula 



/,= / (l + 34'25x 10-^ + 10-7 xlO- 10 * 2 ). 



Above 600° the points are more erratic, but at these higher 

 temperatures the length measurements were somewhat difficult 

 to make ; moreover, as no gas-regulator was available, 



