Facts about Iron. 423 



bules, or bursts violently upwards, carrying with it some 

 hundred weight of the fluid metal, which again falls into the 

 boiling mass below. Every part of the apparatus trembles 

 under the violent agitation thus produced, a roaring flame 

 rushes from the mouth of the vessel, and as the process 

 advances it changes its violet colour to orange, and finally to 

 a voluminous pure white flame. The sparks, which were at 

 first large, like those of ordinary foundry iron, change to small 

 hissing points, and these gradually give way to soft floating 

 specks of bluishlight as the state of malleable iron is approached." 

 As our object is not to write a technical paper on iron manu- 

 facture, we shall refer those who want detailed information 

 on the various projects of the day, to Dr. Percy's work, merely 

 citing his opinion that for the Bessemer process to be " generally 

 applicable in this country, it must be supplemented by the 

 discovery of a method of producing pig-iron, sensibly free from 

 sulphur and phosphorus, with the fuel and ores which are now 

 so extensively employed in our blast furnaces." The doctor 

 adds, " the problem may be difficult of solution, but surely it 

 is not a hopeless one." 



In our domestic economy, broken cast-iron vessels are usually 

 thrown away ; but the Chinese not only make very thin cooking 

 utensils of the cast metal, but dexterously mend holes and 

 cracks. 



Dr. Percy states, on the authority of Dr. Lockhart, how this 

 is done. The Chinese tinker scrapes the surface of the broken 

 vessel clean . He then melts a portion of cast iron in a crucible 

 the size of a thimble in a furnace " about as large as the 

 lower half of a common tumbler." The iron when melted is 

 dropped on a piece of felt covered with charcoal ashes. It is 

 pressed inside the vessel against the hole to be filled up, and 

 as it exudes on the other side, he strikes it with a small roll of 

 felt covered with ashes. The new iron and the old adhere, 

 and when the superfluous metal is removed, the job is com- 

 plete. 



Among the miscellaneous matters of interest in Dr. Percy's 

 book, not the least curious are those relating to the action of 

 sea-water on cast iron, converting it at length into a grey 

 porous mass that grows rapidly hot in contact with air. In 

 1740 some iron guns that went to the bottom with part of the 

 Spanish Armada, were fished up near Mull, in Scotland. On 

 scraping them they soon became so hot that they could not be 

 touched, and a ship surgeon, who was applied to for an eluci- 

 dation of the mystery, suggested that " as they went down in 

 the heat of action they might not have had time to cool, 

 though nearly 200 years had elapsed." 



The alloys of iron are numerous, and special merits are 



