[1] Such disloyalty in trusted servants is one of the most disheartening things that can happen to a public performer. But it must not be thought that I say this out of personal experience: for in the many years that I have been before the public my secret methods have been steadily shielded by the strict integrity of my assistants, most of whom have been with me for years. Only one man ever betrayed my confidence, and that only in a minor matter. But then, so far as I know, I am the only performer who ever pledged his assistants to secrecy, honor and allegiance under a notarial oath. [3] Barnello's Red Demon. CHAPTER SEVEN THE SPHEROIDAL CONDITION OF LIQUIDS.--WHY THE HAND MAY BE DIPPED IN MOLTEN METALS.--PRINCIPLES OF HEAT-RESISTANCE PUT TO PRACTICAL USES: ALDINI, 1829.--IN EARLY FIRE-FIGHTING. TEMPERATURES THE BODY CAN ENDURE. The spheroidal condition of liquids was discovered by Leidenfrost, but M. Boutigny was the first to give this singular subject careful investigation. From time out of mind the test of letting a drop of water fall on the face of a hot flat-iron has been employed to discover whether it may safely be used. Everybody knows that if it is not too hot the water will spread over the surface and evaporate; but if it is too hot, the water will glance off without wetting the iron, and if this drop be allowed to fall on the hand it will be found that it is still cool. The fact is that the water never touches the hot iron at all, provided the heat is sufficiently intense, but assumes a slightly elliptical shape and is supported by a cushion of vapor. If, instead of a flat-iron, we use a concave metal disk about the size and shape of a watch crystal, some very interesting results may be obtained. If the temperature of the disk is at, or slightly above, the boiling point, water dropped on it from a medicine dropper will boil; but if the disk is heated to 340 degrees F., the drop practically retains its roundness--becoming only slightly oblate--and does not boil. In fact the temperature never rises above 206 degrees F., since the vapor is so rapidly evaporated from the surface of the drop that it forms the cushion just mentioned. By a careful manipulation of the dropper, the disk may be filled with water which, notwithstanding the intense heat, never reaches the boiling point. On the other hand, if boiling water be dropped on the superheated disk its temperature will immediately be REDUCED to six degrees below the boiling point; thus the hot metal really cools the water.