Page:Popular Science Monthly Volume 49.djvu/738

716 about two volts. Having constructed his accumulator, Planté experimented with various methods of "forming" the plates that they might yield effects extending over a considerable interval of time. His method was to pass a current through the accumulator first in one direction, then in the other, and repeat this reversal many times with intervals of rest in between. The only current available for this work was that obtainable from a primary battery; this made the process a long and expensive one, but by its means currents of considerable density, lasting for a length of time depending on the extent to which the plates had been affected by the electrolytic process, were obtained. Between 1859 (when Planté began his experiments) and 1880, when Faure invented the pasted battery, great changes had taken place in the condition of the electrical arts and manufactures. The dynamo had been perfected, and offered means for the cheap production of currents of great density and high E. M. F., and hence gave a new stimulus to the production of a practical storage battery. Faure made pastes of red lead and litharge, which he applied to the surfaces of the positive and negative plates. When these were subjected to the forming process, the red lead was oxidized to peroxide and the litharge reduced to spongy lead, with a material saving in time and cost over the Planté process. Almost immediately accumulators were put to a variety of industrial uses, among which may be mentioned their application to carry the day load in lighting stations and to prevent the necessity for running dynamos at night in private residences. Even for traction purposes, where accumulators are subjected to the severest demands, their use was proposed as far back as 1880, and in 1883 a car went into service at Kew Bridge, London, equipped with a Siemens dynamo, set to run as a motor, and about four thousand pounds of batteries. The first storage battery put upon the market was, of course, crude, and the result was that in nearly all of its various applications it was a failure. The modern storage battery dates from the invention of Faure in 1880, and up to within a few years the pasted lead battery was the only form used to any extent. Recently the Planté type has again come into favor, together with an improved form of battery known as the chloride accumulator. The characteristics of the Planté type of battery are capability of giving heavy discharges without sustaining injury, minimum local action, and general freedom from the irregularities due to local action. The chloride battery takes its name from the fact that the active material of the plates is made from lead chloride rather than from metallic lead, as in the Planté, or lead oxide as in the pasted batteries. These cells show a high efficiency in practice, small deterioration, capability of holding a charge over considerable intervals of time, and freedom from short-circuiting, buckling, sulphating, or any of the troubles to which the old lead batteries were subject. They are thus seen to possess none of the defects of pasted batteries, while they embody all the merits of the Planté cells, without their faults of structural weakness and tedious, formation. To-day the extension and use of the storage battery are looked on with growing favor.

Relations of Moisture and Vegetation.—M. Edmond Gain has found, in special researches on the subject, that the influence of moisture on vegetation varies at different periods of growth of the plant, and that alternations of moisture and comparative dryness are more advantageous to it than constant moisture. The plants that require constant moisture as a factor of their most vigorous growth are relatively few. Nearly all plants need water in order to secure vigor of growth, but require it at different intervals in certain precise stages of their vegetation; and plants which at one time take up water with advantage may suffer much from an equal supply at another time. As a rule, the need of water is urgent when the first leaves are appearing. It then diminishes till just before blossoming, when a large supply is called for. This should be suspended after the flowering season is over, for the fruit is best perfected in a relatively dry medium. If the plants blossom more than once, they need a new supply of water previous to the second flowering. In all the author's experiments those plants which were watered at the two critical seasons of first growth and the beginning of blossoming did as well as those which were constantly