70 



CHANGES OF CAST IRON. 



III. 



vas oxided only 

 in the middle. 



Extraft of a Letter from Toulon to General le Vavaffeur, Infpedor 

 of the Materials of the Guns of the French Navy, on the Changes 

 ivhich Cqli Iron undergoes by remaining long in the Sea.^' 



Cad iron lying /\n obfervation I have never heard explained is, that caft: 

 the'bouom^f^ iron, which has lain a long time at the bottom of the fea, is 

 tlu- fea was ox- not equally oxided throughout. I formerly faw a cannon weigh- 

 'j''^'^' . ed up, after it had been funk thirty years, which wasfo much 



r«ot imi- ' ' 1 r • /- 



formly, but in oxided in veins, that I could run a knife into fome places, 

 veins. while the metal clofe by was impenetrable ; and on carrying 



A cannon funk the knife beyond this hard vein, it entered as before. A gun 

 itth'^eSa^cuT-^'* has juft been weighed up here (at Toulon,) belonging to one 

 tion of Toulon of the fhips burnt vvhen the Englifh evacuated the city. The 

 rniddle is fo uniformly oxided, that a large piece may be cut 

 off with a hatciiet. Toward the breech, and toward the mouth, 

 tlie metal appears to have loft nothing of its hardnefs. Can 

 this difference be afcribed to the contact of the fubftances in 

 which the gun was buried underneath the water ? Its pofition 

 at the bottom of the fea not being known, we can form no con- 

 jedtiires on this point. For my part I had imagined, from the 

 hard veins of the cannon mentioned above, that its metal had 

 intermixed with it fubftances on which fait water could not 

 a£t. The gun lately taken out of the fea appeared more ho- 

 mogenous, but I cannot frame any fatisfactory explanation of 

 the fad.f 



* Annales de Chimie, V. 133. 



-j- It is probable, that the laft cannon, as it belonged to a flu'p 

 that was burjied, had part of it heated to fuch a point, when it fell 

 into the fea, as would occafion it to be oxided in a higher degree 

 than the others. It appears to me, more difficult to explain the 

 difFerent veins exhibited by the former cannon. Note of General 

 le Vavaffeur, 



IV. On 



