As noted in the main text, there is an upsurge in the number of titles featuring essay in the plural in our ECCO sampling in the last two decades of the eighteenth century. This increase appears to be tied to an increase in the number of volumes of collected essays. This poses the issue of the relationship of the genre of essay to the genre of collected essays. To aid in future inquiries into the realm of essay, I have supplemented the comparisons of system and essay in the main text with figure B.1 comparing the singular and plural forms of essay.