The class of workers where Johnson place writers of dictionaries is those "who toil at the lower employments of life." This refers to the people with low paying jobs. These people have fears, knowing that they are going to be punished if they don't succeed.
Johnson placed the writers of dictionaries among the lower classes of workers, "lower employments of work".
Explanation:
In his "A Dictionary of the English Language", Samuel Johnson wrote in the preface that writers of dictionaries are "<em>the slave of science, the pioneer of literature, doomed only to remove rubbish and clear obstructions from the paths of Learning and Genius, who press forward to conquest and glory, without bestowing a smile on the humble drudge that facilitates their progress</em>". They "<em>toil at the lower employments of life</em>".
They are sentenced to "<em>diligence without reward</em>" as people only seem to find faults in dictionaries. Their efforts are not appreciated, let alone the appreciation of the work done.
