How does an increase in the price of "non-wage-goods" increase employment? Keynes (1936, Chapter 2) says that based on the classical theory, "there are only four possible means of increasing employment", the fourth of which is:


  an increase in the price of non-wage-goods compared with, the price of
  wage-goods, associated with a shift in the expenditure of
  non-wage-earners from wage-goods to non-wage-goods.


What does the above quote mean? What are wage-goods and non-wage-goods? And why would an increase in the price of non-wage-goods increase employment? 

P.S. Keynes's discussion here is with reference to AC Pigou's Theory of Unemployment (1933), which I can't find online. It seems that Pigou makes a distinction between "wage-goods" and "non-wage-goods". Keynes mentions very briefly that "non-wage-goods" is "Professor Pigou's convenient term for goods upon the price of which the utility of the money-wage depends", but I'm not sure I understand this.
Wage-goods are goods that a worker with wages might buy, perhaps now more commonly called consumption goods

Non-wage-goods are goods that a rentier receiving profits or interest might buy, including what might now be called capital goods or investment goods

As to how to read Keynes's interpretation of Pigou's position (so actually neither Keynes's nor Pigous's), it might be saying that if non-wage-earners shift their demand towards non-wage-goods, this would have the demand-side effect of pushing up the relative price of non-wage-goods and reduce the relative price of wage-goods, with presumably 


either the direct effect of increasing both the number of wage-earners employed producing non-wage-goods and their wages, 
or the indirect effect of increasing the real wage for all wage-earners (since their wage-goods are now relatively cheaper) above the previous "marginal disutility of labour", and this encourages increased wage-earning employment (what today would be called a substitution effect)