Besides the indirect influence of phosphorus, it also has the _direct_ effect of hardening the bronze, because the compounds of phosphorus with copper and tin have a very considerable hardness. These facts, as well as the circumstance that we possess antique bronzes of extraordinary hardness, induced me, with the consent of Baron Sacken, to test the hardness of the bronze weapons in the Vienna Cabinet of Antiquities. Some hard pieces,[25] were sent to Prof. Ludwig, who followed the question with interest and agreed on the method of making the analyses. The results were satisfactory. The bronzes contained traces and up to one-fourth per cent. of phosphorus. Its presence had prevented the formation of oxides in these bronzes, and consequently the weapons were of extraordinary hardness. It now remains to ascertain how the ancients made these phosphorus-bronzes. It is evident that the phosphorus was not put directly into the metal, as is generally done at present. There is another method so simple that we can assume that the ancients employed it unintentionally. I refer to smelting the copper or bronze with charcoal and any salt of phosphorus. In this case the carbon would liberate phosphorus from the phosphoric acid, and it would be taken up by the melted metal. The ancient metallurgists may have made use of the eruptive rocks that contain apatite, and with which copper ores are so often associated, for slag or flux, or the phosphates that occur in the gangue may have been smelted along with the ores; in both cases some phosphorus would get into the metal. Finally it is not impossible that the ancients did not put in phosphorus salts in some form. First of all I would mention certain vegetable and animal substances that are rich in phosphorus, especially _blood_,[26] which was a favorite with the old metallurgists and alchemists as having a powerful enchantment. In each of the cases referred to some phosphorus got into the metal, which thus acquired a considerable hardness that could be increased in the well known manner by chilling and hammering. Under certain circumstances weapons and tools were made almost as hard as steel. We can easily comprehend how bronze with these excellent qualities could compete with steel at a time when rich ores were still abundant, and thus it checked and restrained the development of the iron industry. SUMMARY OF ALLOYS USED BY THE ANCIENTS. _Egypt_.--The wrought metal of the Egyptians is a pure bronze with 6 to 14 per cent. of tin; 22 per cent. is an exceptional case; 1 per cent. of iron is not rare. The Egyptian cast metal is a plumbiferous bronze, with 4 to 11 per cent. tin, and 7 to 12 of lead; in one case 16 per cent. tin; rarely 2 or 3 per cent. of zinc. _Assyria_.--The Assyrian bronze is very pure. It consists of copper, 10 to 14 per cent. of tin, and traces of iron and nickel; in one case 18 per cent. of tin.