Though its effects are similar to those of the Voltaic battery, they are incomparably weaker. Indeed Dr. Wollaston, in using it for chemical decompositions, was obliged to act upon the most minute quantities of matter, and though the result was satisfactory in proving the similarity of its effects to those of the Voltaic battery, these effects were too small in extent to be in any considerable degree applicable to chemical decomposition. CAROLINE. How terrible, then, the shock must be from a Voltaic battery, since it is so much more powerful than an electrical machine! MRS. B. It is not nearly so formidable as you think; at least it is by no means proportional to the chemical effect. The great superiority of the Voltaic battery consists in the large _quantity_ of electricity that passes; but in regard to the _rapidity_ or _intensity_ of the charge, it is greatly surpassed by the common electrical machine. It would seem that the shock or sensation depends chiefly upon the intensity; whilst, on the contrary, for chemical purposes, it is quantity which is required. In the Voltaic battery, the electricity, though copious, is so weak as not to be able to force its way through the fluid which separates the plates, whilst that of a common machine will pass through any space of water. CAROLINE. Would not it be possible to increase the intensity of the Voltaic battery till it should equal that of the common machine? MRS. B. It can actually be increased till it imitates a weak electrical machine, so as to produce a visible spark when accumulated in a Leyden jar. But it can never be raised sufficiently to pass through any considerable extent of air, because of the ready communication through the fluids employed. By increasing the number of plates of a battery, you increase its _intensity_, whilst, by enlarging the dimensions of the plates, you augment its _quantity_; and, as the superiority of the battery over the common machine consists entirely in the quantity of electricity produced, it was at first supposed that it was the size, rather than the number of plates that was essential to the augmentation of power. It was, however, found upon trial, that the quantity of electricity produced by the Voltaic battery, even when of a very moderate size, was sufficiently copious, and that the chief advantage in this apparatus was obtained by increasing the intensity, which, however, still falls very short of that of the common machine.