That is true, I have not given any empirical proof. I would find it pretty hard to supply empirical proof, due to time constraints, therefore I will expand on my reasoning (which you can then contest of course).
I believe that there was relatively few businesses in the 19th century (
premise 1). With 'relatively', I mean relative to the number of people searching for work. Because of this, employers had a lot of "market power" (
http://www.investopedia.com/terms/m/market-power.asp), in my logic this constitutes
conclusion 1, and will function as
premise 2 simultaneously. Most people (including entrepreneurs), pursue financial self-interest up to a certain point (
premise 3). Offering bad working conditions saves money from the employers perspective (
premise 4). This lead 19th century entrepreneurs to offer bad working conditions (
conclusion 2). Premise 1 ensures that workers cannot succesfully search for alternate employment which offers better working conditions (in other words, the labour market was relatively uncompetitive). Hence the workers' response was to form trade unions and thereby increase their own market power relative to employers.