6 books
Duffy's Wave Motor
The Language of Light, or the Mirror of Truth (Classic Reprint)
From Darkness to Light; Or, Duffy's Compendiums of Nature's Law, Forces and Mind Combined in One; Conformable to This His Great Discovery, That the Sun and Earth Are the Poles of the Magnet
The Language of Light; Or Mirror of Truth
The Language of Light
From Darkness to Light