The third and last fish that we shall mention, is the Silurus or Silurus electricus, a genus in Ichthyology belonging to the order of Pisces Abdominales.—The body of this is long, smooth, and without scales, being rather large and flattened towards the lower part. The eyes are of the middle size and covered by the skin which envelopes all the head. Each of the jaws is furnished with a great number of small teeth. About the mouth it has six filamentous appendices, two from the upper, and four from the under lip. The colour of the body is greyish, with a few dark spots towards the tail. With regard to its electrical properties very little is known, enough however to entitle it to the name of electricus. CHAP. XVII. _The influence of electricity on vegetables._ With regard to this part of our subject there has been considerable controversy between philosophers, some of them asserting that electricity is unfavourable, and others that it is advantageous to vegetation. It was asserted by the Abbè Bertholon, in his book entitled Electricitè des meteores, that plants situated near a metallic conductor increased considerably in consequence of their situation. And, on the other hand, Giardini says that plants growing near such conductors are generally unhealthy, and produce very little fruit, but upon removing the conductor the plants become luxuriant and fruitful. The Abbè Bertholon in endeavouring to establish his opinion, constructed what he called an _electro vegetometer_ by means of which the electricity of the atmosphere may be collected in abundance. “This apparatus (says he) having been raised with care in the midst of a garden, the happiest effects were perceived, viz. different plants, herbs and fruits, in greater forwardness than usual, more multiplied and of better quality.” These facts are analogous to an observation that I have often made, viz. that plants grow best, and are more vigorous near thunder rods, where their situation favours their developement. They likewise serve to explain why vegetation is so vigorous in lofty forests, and where the trees raise their heads far from the surface of the earth, so that they seek as it were the electric fluid at a far greater height than plants less elevated: while the sharp extremity of their leaves, boughs and branches serve as so may points granted them, by the munificent hand of nature, to draw down from the atmosphere that electric fluid which is so powerful an agent in forwarding vegetation, and in promoting the different functions of plants.—Such are the theory and experiments of the Abbè, but Doctor Ingenhaus, in two letters to Mr. Molitor, published in the _journal de physique_ for 1786–88 has shewn the fallacy of the theory, by exposing the insufficiency of the experiments upon which it was established. We shall translate a few passages from the Doctor’s letter, which will shew us his opinion and the result of his experiments.