Again, however, the performer picks up another glass, the one with the ammonia, and filling this, it appears to contain wine, but of a lighter color than before. This time, on emptying the glasses into the pitcher, it will appear to be filled again with wine, the ammonia counteracting the effect of the acid. Once more the glasses are filled with wine, all but one, the second acid glass, which the performer has filled. For the last time the pitcher is again filled, and when the contents are poured out there is nothing but water. "For," as the performer remarks, "having begun with water, it is only right we should end with it." As the strength of the various ingredients varies a great deal, the amateur will do well to experiment for the proper proportions of tannin, acid, and ammonia before attempting to exhibit the trick, bearing in mind that the smaller the quantity used the better it will be. Mr. Kellar, who is rather an exhibitor of stage illusions than a sleight-of-hand performer, since his "feats of prestidigitation," to quote the language of the show-bill, are of the most simple character, has made quite a name by offering what he is pleased to call "mental phenomena." In one of the most surprising of these he almost instantly tells the day of the week on which any date of the present century falls. An attempt to explain this has been made by a certain magazine, which seriously informs its readers that "the secret 'of the how' is neither a remarkable 'gift,' nor surprising mental or mathematical ability, as is usually supposed. "The performer holds concealed in his hands tablets on which formulas are engraved, or they may be written on his shirt cuffs. He raises a hand to his head, as though meditating, and can thus, unnoticed, glance over the tabulated formulas. Or he stands before the audience with folded arms, coat sleeves drawn well back, which gives ample opportunity for a quick yet careful glance at the unpretending cuffs; but instead of gazing at the floor in deep thought, as is commonly supposed, he is studying the formula dexterously concealed from the audience." All this sounds very learned, but as there are no less than six tables given as absolutely necessary for the accomplishment of the trick--one of them of thirty-one lines and eight columns--the performer who should attempt it on that plan would require, instead of eyes, what Sam Weller calls "a pair o' patent double million magnifyin' gas microscopes of hextra power." I know of three different short methods of arriving at this calculation, by which any one with a fair memory and an elementary knowledge of mental arithmetic can answer almost instantly the question, On what day of the week does a certain date fall? The easiest and best of these is as follows: First memorize the following couplet: