Civilisation : Its Cause and Cure 



remainder of the sentence will help us. " The 

 temperature is 30 Fahrenheit." * The unknown 

 thing is thirty degrees." What then is a degree ? 

 That is the next question. When the Theory of 

 Heat went out from sensation and left it behind, 

 one of its first landing places was in the expansion 

 of liquids as in thermometer tubes. Here for 

 some time was thought to be a satisfactory register 

 of " temperature." But before long it became 

 apparent that the degree Fahrenheit, Reaumur, 

 or what-not was an entirely arbitrary thing, 

 also that it was not the same x thing at one end 

 of the scale as the other, and finally that the scale 

 itself had no starting point ! This was awkward, 

 so a move was made to the air thermometer, and 

 there was some talk about an absolute zero and 

 absolute temperatures ; it was thought that the 

 Unknown thing showed itself most clearly and 

 simply in the expansion of air and other gases, 

 and that the " degree " might fairly be measured 

 in terms of this expansion. But in a little time 

 this kind of thermometer chiefly because no 

 gas turned out to be " theoretically perfect " 

 broke down, absolute zero and all, and another 

 step had to be made namely, to the dynamical 

 theory. It was announced that the Unknown 

 thing might be measured in terms of mechanical 

 energy, and Joule at Manchester proclaimed that 



1 The very fact alone that the degrees on a thermometer are 

 equal space divisions shows that they must bear a varying relation 

 to the total volume of liquid as that expands from one end of the 

 tube to the other. 



112 



