Fellow Word Nerds Gather Round

I've been drinking deeply from Gadsby's Hymnal. During Saturday's workday I mentioned a confusing section of the preface to a couple of fellas. Any of my fellow word nerds who understand the bolded section, holler at me the next time I see you.

from the preface:
Suffice it to say, that the church and people over which the Holy Ghost has made me overseer, and has been in the constant habit, ever since I came among them, of using Dr. Watts's Psalms and Hymns, Rippon's Selection, and Hart's Composition. But though some of these hymns are big with the important truths of God, there are others, especially among Dr. Watts's and Rippon's, which give as legal a sound as if they had been forged at a certain foundry. This was one reason which induced me to publish a selection. Whole thing is here: