Of all the piles in use, at present, Bunsen's is that most generally adopted, and yet it has two serious inconveniences—it emits nitrous vapors both disagreeable and injurious to the health ; and the electric current, which is very strong at the outset, rapidly decreases in intensity Many liquids, all those, in fact, which are capable of producing oxydation, may be used for the production of electricity, but a solution of bichromate of potash has hitherto been used with advantage instead of nitric acid Bunsen himself was the first to propose the substitution, which has sines been studied by various chemists, especially by Poggendorf, who in 1842 recommended the addition of sulphuric acid to the bichromate, but without obtaining any remarkable improvement; for, although the exhalation of nitrous vapors was avoided, the diminution of intensity was as great as before Poggendorf showed that this was owing to a deposit of oxyd of chromium, with which the charcoal and zinc of the voltaic couple became rapidly coated in the course of the operation, but he was unable to point out any remedy by which it might be prevented M Grenet, a young chemist of Paris, has been more fortunate, and has succeeded in preventing this formation of the oxyd, by the curious expedient of making a strong current of air pass through the pile This current causes the oxyd of chromium to be redissolved in the exciting liquid as soon as it is formed ; the elements of the pile remain unencumbered, and the voltaic current retains the same degree of intensity M Grenet's pile consists of plates of zinc and charcoal placed alternately in a frame provided with vertical grooves into which they fit, so that, as usual, the plates are separated from each other by interstices The zinc plates are all attached to a copper wire acting as a conductor; another conductor of the same material connects together all the plates of charcoal These conductors are coated with an insulating substance The frame has a hollow bottom pierced with small holes, corresponding to the interstices, and a lateral tube fixed to this bottom communicates with the nozzle of a ventilator The exciting liquid, contained in a metal trough, consists of a saturated solution of bicarbonate of potash, acidulated with about onehundredth part of sulphuric acid When the pile is to be used, the frame with the couples which fits into the trough is immersed in the liquid, and the ventilator set agoing As no deposit is formed, the liquid may be kept a considerable time without it being necessary to renew it, or it may be partially renewed from time to time, the great object to be kept in view being, first, the perfect saturation of the liquid, and secondly, the permanent insufflation of air while the pile is being used—Galignani's Messenger