Percy, “seem to be very imperfectly known, and yet none are in my judgment more worthy of the attention of those interested in the history of metallurgy.” The air-tight stove which he describes in his work on _New Observations and Discoveries Respecting Iron and Fire_, published in 1721, is stated to be identical in principle with one recently patented in Washington.[11] Sir Isaac Newton had propounded the corpuscular theory of light, which was for long universally held. Swedenborg dissented, stating, in his _Principia_, that “motion diffused from a given centre through a contiguous medium or volume of particles of ether produced light.” This theory is the one now adopted. Swedenborg also notices that light and electricity are produced by the same efficient cause, thereby supplying the clue to the utilisation of electricity as a means of lighting. Even where in the field of science he was looked upon as a dreamer in his own days, his dreams have since taken practical shape. Among the inventions which he projected was “the plan of a certain ship which with its men was to go under the surface of the sea wherever it chooses, and do great damage to the fleet of the enemy.” He also designed a flying machine, a project which he was very reluctant to drop. Christopher Polhem, however, threw cold water on this, saying, with respect to flying by artificial means, “there is perhaps the same difficulty as in making a _perpetuum mobile_, or gold by artificial means.” His philosophy recognises the synthetical as well as the analytical method as requisite to arrive at true conclusions. “Both,” he says, “are necessary in reflecting upon and tracing out one and the same thing; for in order to do so there is required both light, _a priori_, and experience, _a posteriori_.” “He who is possessed of scientific knowledge,” he says elsewhere, “and is merely skilled in experiment, had taken only the first steps in wisdom. For such a person is only acquainted with what is posterior, and is ignorant of what is prior. Thus his wisdom does not extend beyond the working of the senses and is unconnected with reason; whereas, nevertheless, true wisdom embraces both.” Unquestionably Swedenborg, as he is known to us from the record of the first fifty years of his life (if we except the earliest years of his childhood), was about the last person one would expect to have his name associated with that Swedenborgian gospel by which eventually it came to be known to the world at large. He had, as we have seen, earned many titles to recognition, but assuredly that of a medium of communication between this world and the world of spirits was not one of them.