Blue Ink.
Dissolve a small quantity in a little oil of vitriol, and add a sufficient quantity of water, in which is dissolved some gum arabic.
Scarlet Ink.
Dissolve vermillion in gum water.
A pair of Dice being thrown, to find the number of points on each Dice, without seeing them.
Tell the person who casts the dice to double the number of points upon one of them, and to add five to it, then to multiply the product by five, and add to sum produced the number of points upon the other die. This being done, desire him to tell you the amount, and having thrown out of it twenty-five, the remainder will be a number consisting of two figures, the first of which, to the left, is the number of points on the first die, and the second figure, to the right, the number on the other.
For Example.
Suppose the number of points of the first die which is turned up, to be 3 and that of the other 4, then if to 6, the double of the points of the first, there be added 5, and the sum produced, 11, be multiplied by 5, the product will be 55, to which if 4, the number of points on the other die, be added, 59 will be produced from which if 25 be substracted, 34 will remain; the first figure of which is 3, the number of points on the first die, and the second figure 4, the number of the other.
To make any number divisible by Nine by adding a figure to it.
If, for example, the number named be 72.857, you tell the person who names it, to place the number 7 between any two figures of that sum, and it will be divisible by 9, for if any number be multiplied by 9, the sum of the figures of the product will be either 9 or a number divisible by 9.