A Treatise on the Magnetism of the Needle, the Reasons of it Being North and South, Its Dipping and Variation On the Great Luminary, Or Resevoir of Light, Called the Sun, the Properties of Light : a Reasonable Supposition on the Cause Or Agent, which the Great Author of Universal Nature Employs to Keep the Various Orbs in Their Respective Situations, and Connect Their Influence with Each Other : on the Erroneous Calculation of the Velocity of Light : the Chemical Process which Unintentionally Led to this Investigation