Experiments connected with writing.
Under the heading “Grammar” materials and instruments used in writing are first spoken of, then methods of writing, especially those employed by the wise to conceal their meaning, as when the alchemists use the names of planets to denote the seven chief metals. Instructions are given for making colors employed in illuminating, ink, white tablets, and glues. We are told again how to write letters which are invisible until touched with a rod or exposed to fire. Also how to write so that the writing can be read only in a mirror, how to erase writing without leaving any mark, how to engrave steel and other metals, and how to color the letters so engraved. A paragraph on the right way of speaking might seem to belong under the head of rhetoric rather than of grammar, but just precedes the section of rhetoric in such manuscripts as I have examined. It warns against much speaking, citing Aristotle’s advice to Alexander in the Secret of Secrets, and ends with the familiar couplet:
“If you would be wise, observe my five commands,
What you say, where, of whom, to whom, and when.”[2504]
Riddles: a trick with a knife.
The section on “Rhetoric,” which is defined as speaking ornately, is devoted to riddles, verbal deceits, quibbles, and catches. Under one of its sub-heads, Of Weights, we are told how to balance a knife, although its center is to project beyond the edge of a table and although a weight is to be hung on this projecting end. “The way to fulfill the doctrine of this thing is to fix the blade of the knife in the end of a rod so that it makes an acute angle with the rod, and you will see how the rod will hang with the knife.”
Deceiving the senses.
“Dialectic” is concerned in our treatise not with logical fallacies but with deception of the senses by various tricks. To make water look and taste like wine, a bottle half full of water should be held or left inverted for a time over the orifice of a jar of wine. This procedure is recommended in cases where a patient wants to drink wine and the doctor knows that it would not be good for him. In order to determine whether a patient is really dead and to prevent cases of burial alive, it is recommended to hold a mirror to his nostrils and see if it will be clouded by a faint breath. This comes under the sub-head, De olfactus deceptione, breathing as well as the sense of smell evidently being included under the olfactory organs. The sense of hearing is deceived by an echo, and the sense of sight by mirrors which enlarge or multiply objects or make an image appear outside the mirror. The use of burning glasses is also discussed.
Tricks of jugglers.
Under the sub-head, “Sophistries called sleight-of-hand,” (De sophisticationibus que vocantur iugulationes), come the tricks or cautelae of the jugglers. An apple is made to move on a table by preparing a hole in the center beforehand and placing a beetle inside. To construct a cross that will seem to turn to right or left automatically in answer to questions put to it concerning hidden or future matters, one builds it up of wax about the tail of some insect or tiny animal[2505] which is also concealed in wax and irritated with sage[2506] so that it wiggles its tail and the cross. Hands that have been bound may be freed by cutting the rope against a prearranged knife. Again we meet the experiments to make cooked meat seem raw or full of worms and directions for blowing soap-bubbles, a process which is spoken of as “making a golden sphere appear flying in the air.” Other illusions under “Dialectic” are to seem on fire and not be burned, to see stars in the daytime by multiplying the reflections of the sun, to make a silver coin seem copper, and to deceive the sense of touch by such methods as holding an object between two crossed fingers.