A frequent disease of bronzes is the formation of small granules of translucent bright green rust. This is attributed to an organic growth, which is infectious, and may spread through a collection. One of the worst instances I dipped in carbolic acid, and this absolutely stopped the attack, proving that it is not due to action of chlorine. But we must not take this as a certain proof of the organic nature of the mischief, in view of the inhibitory effect of anæsthetics, etc., in stopping electric and chemical action.
Lead.
Lead is usually coated with white carbonate, the outer face of which shows more than the metallic surface beneath. It should therefore be let alone; but if it shows signs of further changes, due to salts in it acting with damp, then soaking in several waters will probably make it safe. If carbonate continued to be formed, I should try saturating with paraffin wax.
Iron.
Iron can seldom be cleaned; but if it has only a little superficial rust, this may be removed by placing it in the strongest nitric acid, which dissolves the oxide but renders the iron passive. For ordinarily rusted iron all that can be done is to arrest further changes. A long soaking in water to remove all salts, and then baking dry and saturating with wax, is a safe treatment and always available.
Sorting.
Sorting and joining fragments is sometimes very essential. In the royal tombs of the Ist Dynasty we collected thousands of pieces of stone bowls and vases. Only a very small number out of such cartloads of fragments were of value as they lay; but so far as they could be reconstructed they gave an important series of forms. To extract any result it was needful to place together all the pieces that belonged to each separate vase; and the same work frequently had to be done on a lesser scale in dealing with groups of broken stone and pottery. Taking the whole of the fragments which can be supposed by their position to belong together, they are first sorted over for quality, making as many divisions as are quite safe to be distinguished one from the other, so that there shall be no chance of parts of one bowl being classed in two different divisions. All the pieces of one division, sometimes as many as 500 of one quality, are then to be laid out on tables,—the pieces of brim placed at the top of the tables, and classed according to form and curvature; the pieces of middle of the vase along the middle of the table, all carefully laid with the axis vertical; the pieces of base at the nearer edge of the table, classed according to diameter. Taking then the first piece of brim, it is held at each end of each other piece to which it can possibly belong; every possible fit is thus found. Each piece of brim is to be thus tried with all that follow it, those before it having been already tried with it. When all the possible junctions of brim have been made, then a row of joined brim pieces are to be laid on a board, and the angle which each broken edge makes with the vertical is to be looked for among all the broken sides of the middle pieces, looking for such slope at both upper and lower sides if the tops are not distinguishable from the bottoms of the pieces. Thus, say the first broken edge of brim slopes at
20°, every piece broken at 20°
