1377sulated with sealing wax. Although there may be a slight effect of this distance of 8 cm. from center to center, as compared with 0.5 em. in the first case described, yet the effect is so small as to be fairly negligible. As the current density representing the extent of corrosion that occurs in a tin can must be exceedingly small, it is not likely that the conductivity of the electrolyte and hence the distance of two electrodes that might be set up within a can of fruit are pronounced factors in determining the rate or nature of corrosion. Application of Results t o Commercial ExperienceThe effect, from the standpoint of corrosion in canned fruits, in plain tin cans, as compared with that in enameled cans, is very striking. The purpose of enameled cans should be borne in mind. Enameled cans are used for colored fruits whose color is bleached by their action on plain cans. The bleaching action in plain cans is evidence that the coloring matter enters into the corrosion. The fruits which are generally packed in plain cans, as well as those which are ordinarily canned in enameled cans, do not tend to perforate unenameled cans, although the colored fruits generally have a tendency to perforate enameled cans. The action of the fruit on an unenameled can is generally distributed over the entire area of the can. In plain cans the area of tin exposed always enormously exceeds the area of iron exposed. The effect of the anodic tin in inhibiting iron corrosion is therefore pronounced, while the effect of the small area of cathodic iron exposed is almost negligible in increasing the amount of tin corrosion.In an enameled can a different condition exists. A vast proportion of the area of tin is eliminated from the corrosion picture by the enamel coating. It is true that portions of the iron which the tin does not coat may also be covered by the enamel coating. However, it is a t that portion of the can which is adjacent to the seam and other points where the plate undergoes a strain in forming the can that the bulk of the corrosion occurs. At such points both the enamel coat and the tin coat tend to be more or less fractured. At such points, therefore, the relative areas of tin and iron are of a vastly different proportion than in an unenameled can. At such points in an enameled can the area of the exposed iron apparently is sufficient to materially influence corrosion of the anodic tin. It is a common observation that such areas are, relatively early in the life of the can, completely detinned. The result is that, comparatively early in the life of many enameled cans, the area of iron exposed actually exceeds the area of tin exposed. The exposed iron, therefore, loses to a considerable extent the protective effect of the anodic tin. Local couples no doubt are set up on the iron, augmented by its non-homogeneous nature, whereby hydrogen is formed, and eventually pitting and perforation result. At any rate, it is common commercial experience that enameled cans give rise to hydrogen formation and perforations to a much gr...

Several modifications of an apparatus are described which derive heat energy from their environment and dissipate it as latent heat in water vapor. Visible work is done. It is suggested that they may be used in high-school science classes to demonstrate the energy changes and the resulting differences in vapor pressure and hydrostatic pressure upon which their activity depends.