1839. The galvanic plant protector was supposed, when it was first invented, to afford a secure protection against slugs and all other similar animals; and the theory of its construction is very curious. It consists of a taper or conical ring of zinc, the top edge of which is flanged off about a quarter of an inch, and cut into numerous zigzag or vandyked points. Immediately under this pointed flange, another ring, but of copper, is neatly fitted, being exactly of the same taper as the former, and fully an inch broad, supported in its place by dots of solder in three or four places of its circumference. It was supposed that any snails and slugs that might crawl up the side of the pot would receive a galvanic shock the moment they left the zinc and reached the copper. But, however ingenious this plan appears in theory, it was not found to answer in practice, and it is now very seldom to be met with.