This beautiful experiment can be performed by any person in possession of a common galvanic battery. The process is as follows: - Soften a piece of gutta percha over a candle, or before a fire; knead it with the moist fingers upon a table, until the surface is perfectly smooth, and large enough to cover the leaf to be copied; lay the leaf flat upon the surface, and press every part well into the gutta percha. In about five minutes the leaf may be removed, when if the operation has been carefully performed a perfect impression of the leaf will be made on the gutta percha. This must now be attached to the wire in connexion with the zinc end of the battery (which can easily be done by heating the end of the wire, and pressing it into the gutta percha), dusted well over with the best black lead, with a camel's hair brush - the object of which is to render it a conductor of electricity - and then completely immersed in a saturated solution of sulphate of copper. A piece of copper attached to the wire in connexion with the copper end of the batten-, must also be inserted into the copper solution, facing the gutta percha but not touching it; this not only acts as a conductor to the electricity, but also maintains the solution of copper of a permanent strength. In a short time, the copper will be found to creep over the whole surface of the gutta percha, and in about twenty-four hours, a thick deposit of copper will be obtained, which may then be detached from the mould. The accuracy with which a loaf may thus be cast is truly surprising. I have in my possession a cast of a hazel-leaf made by the process, which nobody would take to be a production of art; every fibre and nerve, in fact, the minutest part, is delineated with the ut most fidelity.