612 Dr. J. H. Gladstone [Feb. 11, 



made to imitate gold, of which aurochalcnm is an instance, and that 

 may have been yellow brass. 



As to oxygen. It is generally supposed to exist in copper in the 

 form of the red cuprous oxide ; and most of the copper, and many of 

 the bronze, implements have a covering of this substance. This is 

 caused by the gradual formation of an oxychloride of copper through 

 the action of alkaline chlorides in the soil, aided by the air and 

 moisture. Berthelot has worked out the chemistry of this substance 

 very fully, and shows how when once formed it gradually works its 

 way into the solid metal, transforming it into the suboxide, and 

 frequently disintegrutiug it. Some good specimens of little bronze 

 images suffering this disintegration are exhibited by Mr. Joseph Offord. 

 Two at least of the copper adzes on the table consist to the extent of 

 30 or more per cent, of oxide of copper; they are exceedingly hard, 

 and it becomes a question whether the formation of the oxide is due 

 to the slow chemical change, or whether it was purposely produced 

 in the manufacture in order to harden them. The effect of different 

 proportions of oxygen on the tenacity of copper is known to be very 

 various, and certainly deserves further investigation. 



It is difficult, or rather impossible, to express in definite figures 

 the advantage gained by the ancient Egyptian metallurgists through 

 this alloying of the copper. Arsenic, tin or zinc may and do affect 

 the hardness, or the tenacity, or the elasticity, in different ways, and 

 also according to the proportion of the metal united with the copper. 

 Thus, there are several very different kinds of alloys of copper and 

 tin, though they are all included under the name of bronze ; more- 

 over, a piece of copper which has been exposed to a considerable 

 stress, is permanently altered in its properties. Again, in any table 

 of numerical values, it should be taken into account whether the 

 copper with which the alloys are compared had been made as pure 

 as possible, or contained a normal amount of oxygen.* We must 

 rest contented with the knowledge that copper can be rendered 

 stronger and more serviceable by these means, and that the ancient 

 artificers were acquainted with the fact. 



Alter the extensive use of copper and bronze in ancient Egypt, 

 other metals were gradually employed. Silvtr, as distinct from 

 electrum, seems to have been little used, except for ornamental 

 purposes.! The diadem of one of the kings named Antef (b.c. about 



* For tabulated results of experimf-Vits bearing on these points, see * The 

 Testing of Materials of Constructiuu,' by Prof. Cawthorne IJnwin ; and the 

 second Report to the Alloys Reseai eh Corandtteo of the Institution of Mechanical 

 Engineers, by Prof. Roberts-Austen, witii the discussion thereon. —Proc. Inst. 

 Mi'ch. Eng. April 1S98. 



t In tlie translation of 'The Book of the Dead,' by Dr. Wallis Budge, 

 vol. iii. published since the lecture, it appears that in one of tlie oldtst chapters, 

 said to have been found by Herutataf, about B.C. 3600, there is a formulary to 

 be said over a scarab of greenstone encircled with a band of refined copper, and 

 having a ring of bilver. 



