and incorrect opinions, chiefly of a mystical character.  If, for instance, it was observed that a flag and a fern never grew near each other, the circumstance was imputed to some antipathy between these vegetables; nor was it for some time resolved by the natural rule, that the flag has its nourishment in marshy ground, whereas the fern loves a deep dryish soil.  The attributes of the divining-rod were fully credited; the discovery of the philosopher’s stone was daily hoped for; and electricity, magnetism, and other remarkable and misconceived phenomena were appealed to as proof of the reasonableness of their expectations.  Until such phenomena were traced to their sources, imaginary and often mystical causes were assigned to them, for the same reason that, in the wilds of a partially discovered country, according to the satirist,

“Geographers on pathless downs
 Place elephants for want of towns.”

This substitution of mystical fancies for experimental reasoning gave, in the sixteenth and seventeenth centuries, a doubtful and twilight appearance to the various branches of physical philosophy.  The learned and sensible Dr. Webster, for instance, writing in detection of supposed witchcraft, assumes, as a string of undeniable facts, opinions which our more experienced age would reject as frivolous fancies; “for example, the effects of healing by the weapon-salve, the sympathetic powder, the curing of various diseases by apprehensions, amulets, or by transplantation.”  All of which undoubted wonders he accuses the age of desiring to throw on the devil’s back—­an unnecessary load certainly, since such things do not exist, and it is therefore in vain to seek to account for them.  It followed that, while the opposers of the ordinary theory might have struck the deepest blows at the witch hypothesis by an appeal to common sense, they were themselves hampered by articles of philosophical belief which they must have been sensible contained nearly as deep draughts upon human credulity as were made by the Demonologists, against whose doctrine they protested.  This error had a doubly bad effect, both as degrading the immediate department in which it occurred, and as affording a protection for falsehood in other branches of science.  The champions who, in their own province, were obliged by the imperfect knowledge of the times to admit much that was mystical and inexplicable—­those who opined, with Bacon, that warts could be cured by sympathy—­who thought, with Napier, that hidden treasures could be discovered by the mathematics—­who salved the weapon instead of the wound, and detected murders as well as springs of water by the divining-rod, could not consistently use, to confute the believers in witches, an argument turning on the impossible or the incredible.