that no suspicion could be entertained as to the metal of which they were really formed. In the case of medallions I sometimes put into the solution some crystals of distilled verdigris, which produced a good imitation of antique bronze. Several specimens of these bronzed medals and copper-coated castings of natural objects were exhibited by me at Topliss' Museum of Arts and Manufactures, which at that time occupied the present site of the National Gallery in Trafalgar Square. Among the things I exhibited there were a basso-relievo of one of the cartoons of Raphael, a large medallion head of St. Peter, and several smaller casts of medals. I also exhibited a group of three prawns lying on a large grape-vine leaf, a moss-rose bud with leaves, and a beautiful piece of Scotch kale, the intricate convolutions of which appeared to all who saw it a thing impossible either to mould or cast, but which was nevertheless a comparatively easy one, because this vegetable leaf is very thick and succulent, and consequently leaves scarcely any ash in the mould when burned.

I may mention that various devices were tried to get rid of the fine ash resulting from the burned vegetable matter.

Sometimes small passages open to the outer air were left in the mould, and into these a blast of air was blown to assist the combustion and destruction of the vegetable matter while still in a red-hot state. At other times the mould, when cooled down, was filled with a strong solution of nitre, which saturated the dried vegetable matter. The remainder of the fluid was then poured out and the mould again made red- hot, when the nitre, causing complete combustion, reduced the contents to a fine white ash. When the mould had again cooled down, the ash so formed was floated out of it, by pouring mercury in and well shaking it.

In fact, the treatment resorted to for cleansing the mould had to be adapted, in each case, to the nature of the object to be destroyed and got rid of.

I had a strong belief that the mode I have described, of reproducing the most delicate and, at the same time, the most intricate vegetable forms, might be utilised by botanists and other collectors, in remote or solitary places, from whence the transmission of such objects in their natural state would be impossible. It would be perfectly easy for the botanist to take abroad with him a few tin cans filled with the dry powdered materials required for his moulds, ready to be mixed with water at a moment's notice. A number of small cardboard boxes, painted in oil colour so as to render them waterproof, and fitting inside each other, would enable him to choose one suitable in size, for any particular specimen to be moulded in. He would have nothing to do but to mix with water a small quantity of his prepared plaster, place the delicate fungus, lichen, or other specimen, in the bottom of the box, and pour in the semi-fluid mixture, filling the box, and gently tapping its sides and bottom to ensure the penetration of the fluid matter into every interstice of the specimen. In less than a quarter of an hour, he would find in his fragile little box a hard, solid, square mass, in which the specimen would be safely embedded, where it might remain uninjured for any necessary period, and then be burnt out, and the object reproduced in metal. An absolutely perfect copy of nature's most beautiful work, in an indestructible material, would thereby be obtained by a minimum of labour and cost.

I made many attempts to impress the importance of these facts on some of the managers of the British Museum, with whom I had several interviews, but all to no purpose; and so the whole thing dropped, and I had all my trouble in vain.

Returning from this digression, I may state that the site occupied by Topliss' Museum was required for the erection of the present National Gallery.*³ A museum was, however, erected in Leicester Square, where the Panopticon was subsequently built, and it was to this new home that my specimens of casting were removed.

About the year 1836 I made the acquaintance of Dr. Ure, author of the well-known Dictionary of Arts, Manufactures, and Mining, and of him I can only speak with affectionate regard. I had sought his assistance in some analyses, and after several interesting interviews he furnished me with the information I desired,