working with them diligently like so many emmers (pg. 13) -- Emmer is a kind of wheat, can't find another meaning.
furze bush (pg. 61) -- A Gorse bush. Spiny, spiky, stickery!!
Philadelphia Experiments (pg. 175) -- Ben and his son William flew a kite in a storm.
grampus (pg. 247) -- A killer whale, probably.
fizgig (pg. 247) -- A fish gig, harpoon, or fish spear.
So convenient a thing is it to be a reasonable creature, since it enables one to find or make a reason for every thing one has a mind to do. -- (pg. 41)
...Temple of LEARNING: Every Peasant, who had wherewithal, was preparing to send one of his Children at least to this famous Place; and in this Case most of them consulted their own Purses instead of their Childrens Capacities: So that I observed, a great many, yea, the most part of those who were travelling thither, were little better than Dunces and Blockheads. Alas! Alas! -- (pg. 201)