Who did the author of "factory life as it is, by an operative" say were being shackled into riveted " chains of physical . . slavery"?

The Factory of Life As It Is. By an Operative is a campaign to improve the working conditions of American women workers in 1845. The bustling industry of textile led to the opening of factories that employ women for textile production laboring in the mills. Workers run the mill for 13 hours and this led to demoralization of women workers and subsequently, a violation of their human rights. 
Those who are "shackled into riveted chains of physical slavery" are the Lowell Women workers who toil for 13 hours, running the mill day and night.