VOL. LXXXVI.] PHILOSOPHICAL TRANSACTIONS. 01 



steel ; because they consist of carbon and iron ; because they are capable of indura- 

 tion by plunging them when ignited in a cold medium; and they are softened by 

 ignition and gradual cooling; they have the colour, texture, hardness, brittleness, 

 malleability when ignited, and specific gravity of many sorts of steel. 



2. The sword, fig. 8, appears to be the hardest; and the dagger, fig. 11, the 

 softest steel of the above instruments. 



3. These steel instruments appear to have been tempered, at least in the parts 

 destined for cutting and piercing. 



4. The axe, fig. Q, being all steel, affords a proof that the ancients were not ac- 

 quainted with the art of manufacturing soft malleable iron: nor consequently of 

 welding it with steel; and that the only state of iron which they used, and could 

 manufacture, was steel. 



5. Though it is most probable that these steel instruments were made of steel 

 got directly from the ore, they show that the ancients could render such steel very 

 malleable in its ignited state; and free from extraneous matters, and particularly 

 from oxygen. 



6. The different degrees of hardness and brittleness of these instruments may 

 reasonably be imputed to the different proportions of carbon which they contain; 

 and to the different degrees of cold applied in tempering them ; though the expe- 

 riments were not made with such precision as to demonstrate the reality of these 

 assigned causes. 



7. It seems probable that the axe was tempered at a low temperature, and had 

 been much hammered: hence its great specific gravity before hammering, and 

 the little increase of its specific gravity by further hammering; and hence the 

 great diminution of its specific gravity by quenching in its state of ignition to 

 whiteness. 



8. Iron and steel instruments are destroyed, commonly, by the oxygen of water, 

 or oxygen of atmospherical air. The destruction of iron instruments is prevented 

 by whatever prevents the union of the oxygen of these substances. On this prin- 

 ciple the sword, fig. 8, was preserved by its varnish ; but the other tools must have 

 owed their preservation to their having been accidentally coated with earthy matter; 

 which perhaps contained principally clay. 



9. The destruction of the iron sword by oxygen within the copper scabbard; 

 and the preservation of the part of it not in contact with the copper, is a good ex- 

 ample of the action of copper and water united in destroying iron, the copper 

 remaining entire. This effect of copper on the iron bolts and nails, in copper-bot- 

 tomed ships, is a loss of the greatest magnitude. Fig. 10, is another sword of the 

 same kind as fig. 8, in Sir Jos. Banks's collection. 



XIX. On the Periodical Star a. Herculis ; ivith Remarks tending to establish the 

 Rotatory Motion of the Stars on their Axes. To which is added a Second Cata- 

 logue of the Comparative Brightness of the Stars. By Wm. Herschel, LL.D. } 

 F. R. S. p. 452. 

 In my first catalogue of the comparative brightness of the stars, I announced <» 



