"The Mystery of Printing and the Magnet"

I've recently discovered a really excellent blog called Early Modern Whale, from Royal Holloway lecturer Dr Roy Booth. Dr Booth blogs about 17th century English texts, and he has a habit of ferreting out sources which make the period sound really quite surreal.

(Some examples:
A 1674 pamphlet graphically arguing that coffee causes men to become impotent and 'Frenchified'

A wonderfully petty-sounding squabble between two professional astrologers

A pamphlet relating the "true discourse" on one Stubbe Peeter, alleged werewolf and demonologist

More astrology plus, in the comments, the following gem:

"'Arise Evans had a fungous nose, and said, it was revealed to him, that the King's hand would cure him, and at the first coming of King Charles II into St. James's Park, he kissed the King's hand, and rubbed his nose with it; which disturbed the King, but cured him'." -John Aubrey)

But since I've been looking at missionary history lately, I'm more specifically interested in this passage. This is from A Collection of letters and poems: written by several persons of honour and learning, upon divers important subjects, to the late Duke and Dutchess of Newcastle (published 1678). Specifically, it's from a letter which Joseph Granvill wrote to the Duchess as part of an attempt to persuade her of the reality of witchcraft. In response to the Duchess' counterargument that witches go unmentioned in the New Testament, Granvill replies:

"Negative Arguments from Scripture use not often to be of any great signification or validity. Our Saviour spake as he had occasion, and the thousandth part of what he said, or what he did, is not recorded, as one Evangelist intimates. He said nothing of those large unknown Tracts of America, gives no intimations of the Existence of that numerous People, much less any instructions about their Conversion. He gives no particular account of the affairs and state of the other World, but only that general one, of the happiness of some, and the misery of others. He makes no discovery of the Magnalia of Art, or Nature, no not of those whereby the propagation of the Gospel might have been much advanced; viz. The Mystery of Printing, and the Magnet. [...] I confess the omission of some of these particulars is pretty strange and unaccountable, and an argument of our Ignorance of the Reasons and Menages of Providence, but I suppose of nothing else"

I'm guessing, though not certain, that the 'mystery of the magnet' refers to the invention of compasses, and hence the means to navigate to the Americas. But I guess I hadn't really considered the difficulty that early missions to the Americas would have faced in trying to adapt Biblical evangelism to their new situation. I wonder whether Granvill ever reached any conclusions about why the gospels had opted to remain silent on the topic.