The archæology and prehistoric annals of Scotland

by Sir Daniel Wilson

The synthetic experiments of Dr. Pearson furnish the following results applicable to the present argument:—The bronze relics submitted to analysis and comparison consisted—1. of a lituus, or musical wind-instrument, found in the river Witham, Lincolnshire, in 1768; 2. A spear-head of the common unperforated form, "made of cast metal, as appears from its rough surface, figure, texture, and grain.... It is open grained almost as copper, and porous, as if made of bad metal, of a blackish-brown or dark-grey colour;" 3. A sauce-pan, (Anglo-Roman patella,) also made of cast metal, open grained, impressed on the handle with a stamp, C. ARAT.; 4. A bronze scabbard, with a sword of iron within it, thought to be Danish; and, 5. Three celts, (Nos. 1 and 3, what we now term axe-heads, No. 2 an axe-shaped palstave,) all found in the bed of the river Witham. In his comparative experiments Dr. Pearson fused fifty grains of tin with 1000 grains of copper; i.e., one part of tin to twenty parts of copper. The result, when polished, differed in shade of colour from that of the celt metals, being much darker—a point not unworthy of note in determining some of the characteristics of primitive bronze relics. Its fracture shewed a colour inclining to the peculiar red of copper. One hundred grains of tin united by fusion with 1500 grains of copper; i.e., one part of the former to fifteen parts of the latter, resembled the celt metals, Nos. 1 and 2 in colour, polished surface, grain and brown colour of the fracture, the red of the copper being no longer apparent. It was stronger than the celt metals, but not so hard, while it was harder than the spear-head and the patella. No very remarkable differences are observable in the experiments of the combinations of twelve, ten, nine, and eight parts of copper with one of tin. When, however, the copper is reduced to seven parts to one of tin, the increase in hardness and brittleness becomes very apparent, while the alloy is decidedly paler in colour. The same characteristics were still more marked on successively reducing the proportions of copper to seven, six, five, four, and three; and when an alloy was made of two parts of copper with one part of tin, it "was as brittle almost as glass." It is not difficult, from these results, to imagine the process pursued by the old worker in bronze, who, having ascertained that he could harden his copper by alloying it with tin, would not fail to diminish the added quantities of the latter till he had secured an efficient practical admixture for the purposes of his manufacture, in which it is apparent, from the above results, that no very great nicety of apportionment of the ingredients was required. The most fit proportions for the manufacture of weapons and tools Dr. Pearson considers to be one part of tin to nine parts of copper.

The result of a comparison of numerous analyses of primitive bronze relics will, I think, lead to the conclusion that their correspondence is not greater than might be anticipated to arise from the experience acquired by isolated workers, when dealing with the same metals, with similar objects in view, while the frequent presence of other metals besides tin and copper may, in the majority of cases, be accepted as additional proof of the unsystematic processes of the old metallurgist; though in some instances we may trace, in the adaptation to a special purpose, the evidence of design.

The results of Dr. Pearson's analytic experiments are as follows:—

The Lituus contained a little more than twelve per cent. of tin; i.e., about one part of tin to seven and a half parts of copper. Specific gravity, (before melting,) 8.3.

The Spear-head; fourteen per cent. of tin, or somewhat less than one part of tin to six parts of copper; in addition to which it contained the proportion of fifteen grains of silver in a troy pound of the mixed metal. Specific gravity, 7.795.

The Patella; a little more than fourteen per cent. of tin, or about one part of tin and six parts of copper. Specific gravity, 7.960.

Bronze Scabbard; a little more than ten per cent. of tin, or about one part of tin to nine parts of copper. Specific gravity, 8.5.

Celts, Nos. 1 and 2; a little more than nine per cent. of tin, or about one part of tin to ten parts of copper. Specific gravity, No. 1, 8.780; No. 2, 8.680; No. 3, a little more than twelve per cent. of tin, or about one part of tin to seven and a half parts of copper. Specific gravity, (after melting,) 8.854.

In the month of August 1816, some labourers employed in lowering the road on the top of a small eminence, called Huckeridge Hill, near Sawston, Cambridgeshire, discovered the remains of a human skeleton, at the feet of which stood two large bronze vessels. On the left side of the skeleton were also found an iron sword greatly corroded, and fragments of a very coarse urn, half an inch in thickness. The rim of the largest bronze vessel was ornamented with a row of bosses, indented from the under side. Dr. Clarke, Professor of Mineralogy in the University of Cambridge, subjected portions of the bronze to analysis, and communicated the result to the Society of Antiquaries of London. The conclusion he arrived at was, that they consisted of 88/100 of copper with 12/100 of tin, or about one part of tin to seven and a half parts of copper. Dr. Clarke also assigns exactly the same proportions of copper and tin as constituting the bronze coinage of Antoninus Pius, and of his successor Marcus Aurelius; which it will be seen correspond with those of the lituus and one of the celts analyzed by Dr. Pearson. The process adopted by the former, however, in the chemical analysis of those bronzes is much less satisfactory than that of Dr. Pearson, as he appears to have assumed the absence of all other metals, and sought only for copper and tin.[284] A bronze sword, found in France, proved on analysis to contain 87.47 parts of copper to 12.53 of tin in every 100 parts, with a portion of zinc so small as not to be worth noticing, or capable of affecting the bronze.[285] The analyses of various specimens of antique bronze, including a helmet with an inscription, found at Delphi, and now in the British Museum, some nails from the Treasury of Atreus at Mycenæ, an ancient Corinthian coin, and a portion of a breastplate or cuirass of exquisite workmanship, also in the British Museum, are stated to have afforded about eighty-seven or eighty-eight parts copper to about twelve or thirteen of tin per cent.[286]