IV.—PORTION OF A BRONZE SWORD. (No. 546.)
The weight of the specimen, inclusive of the incrustation, was 585 grains; it was about 1½ inch in length, and varied from about 5-8ths to 7-8ths of an inch in thickness. A sketch of a section of the specimen is annexed.
No. 546.
Piece of a Bronze
Sword. Sepulchre IV.
Dimensions stated in
fractions of an inch.
The whole of the specimen was coated with an irregular layer or layers of matter, varying in chemical and physical characters and in thickness. In the centre, where the crust was removed, the solid metal varied from about 4-8ths to 5-8ths of an inch in thickness.
DR. PERCY'S ANALYSIS.
One side was chiefly incrusted with irregular patches of dull earthy non-crystalline matter, of varying shades of green and brown, which were found to consist of green carbonate and oxychloride of copper in different proportions; a few minute pale green needle-like crystals were noticed on the other surface; there were also observed irregular thin layers or patches of green (found to be green carbonate of copper, in some places containing more or less of oxychloride of copper) and blue crystals (found to be blue carbonate of copper) of varying tints and lustre. One end of the specimen was covered with a dark green crust with a velvety lustre, which was found to consist of minute transparent crystals of oxychloride of copper; the opposite end, which was flat, and had the appearance of having been cut or rubbed, was chiefly coated with deep red non-crystalline red oxide of copper; and a depression on the surface was lined with the dark green velvety crust; on the edges, where the outer part of the crust had been broken off, was a dull white opaque layer of peroxide of tin, and on either side of it were layers of dark red compact red oxide of copper, having cavities here and there filled with ruby-red brilliant transparent crystals of the same substance. When the outer incrustation had been subsequently removed, these substances were found to extend more or less over the surface underneath.
The specimen was cut across in the centre when portions of the incrustation were detached; by this means the structure of the specimen, and the nature of the substances forming the incrustation, could be well observed. The substances were generally found to occur in the following order, from within outwards.
I.—Solid metal.
II.—Particles of metal resembling filings, tarnished on the surface, and intermixed more or less with a dull greenish-grey substance, which was found to contain chlorine, copper, and tin.
III.—A pale green dull soft compact layer, which was found to consist chiefly of carbonate of copper, containing chlorine, probably in combination as oxychloride of copper, and a little peroxide of tin.
IV.—Red oxide of copper, varying in colour from brick-red to dark red, compact, dull and opaque, and in part crystalline.
V.—Peroxide of tin: examined under the microscope it was found to be veined with minute thin layers of red oxide of copper.
VI.—Red oxide of copper similar in character to No. IV.
VII.—Irregular patches of amorphous and crystalline substances of various shades of green, blue, and brown, as before described.
The above order of superposition was not always observed; thus, in some places there was a layer of red oxide of copper in No. III.
When the incrustation had been removed by sawing the specimen across the middle, and filing, the metal was found to be very sound and free from cavities. The fracture was yellowish copper red, and finely granular.
Portions of the solid metal perfectly free from incrustation were selected for analysis.
COMPOSITION PER CENT.
| I. | II. | Mean. | |
|---|---|---|---|
| Copper | 86·41 | 86·31 | 86·36 |
| Tin | 13·05 | 13·07 | 13·06 |
| Lead | — | 0·11 | 0·11 |
| Iron | 0·17 | — | 0·17 |
| Nickel | 0·15 | — | 0·15 |
| Cobalt | traces | — | traces |
| 99·85 |
The specific gravity of the metal was 8·858 at 60° Fahr.
A portion of clean solid metal weighing 24·811 grains was employed for the experiment.
The substances forming the incrustation could not possibly be separated from each other with sufficient accuracy to allow of their being separately analysed.