420 Encrustation of Steam Boilers in India. [No. 5. 



A curious variety of metallic deposit sometimes occurs on the steam 

 pipe, close to its connection with the cylinder, when the boiler is of 

 iron, the pipe of copper or mixed metal containing copper, a specimen 

 of this accompanies this paper.* It is about half an inch thick, and 

 consists of alternate layers of pure copper, about forty in number, and 

 of copper slightly oxydized. This was found in the steam pipe of the 

 P. and O. S. N. Co.'s Steamer Pekin, which connected the fore and 

 after boilers together : the boilers are iron, the connecting pipe copper. 

 There is a considerable scale of rust on the plate through which the 

 pipe passes : there are lead joints between the copper and the iron, to 

 prevent or diminish the action of the metals on each other. The 

 copper crust was found immediately inside the stop valves and extended 

 about a foot into the pipe. The same action is believed to be going 

 on in all the copper pipes, but in this case it was collected by the 

 self-action stop valves : in the other cases the cupreous solution flowed 

 into the boiler or cylinder, and was lost. For the specimen now sent 

 I am indebted to Captain Gribble, and for the information regarding it 

 to Captain Baker, of the Pekin. 



It is quite clear here that a complex series of chemical processes 

 must have been going on to produce this beautiful specimen of Electro- 

 type copper, which was soft, and cut like black lead when first received, 

 though it has now assumed its proper hardness. We must first have 

 had the copper dissolved by the steam or water in the pipe, the solu- 

 tion collected beyond the stop valve must have been revived by galvanic 

 action induced by the copper and iron on each other. It is probable 

 that each layer was due to a single working of the boilers, and that 

 the open film between was produced when the steam was down. No 

 similar deposit has ever been met with by any of the Engineers I have 

 seen. 



* Deposited in the Museum of the Asiatic Society. — Eds. 



