672 , transactions of the 



Polytechnic Association of the American Institute, ) 



February 29, 1860. j 



R. P. Stevens, M. D., Cliairman. John Johnson, Esq., Secretary pro tern. 



Mr. Babcock gave an account of a case of the deterioration of cast iron, 

 which he could not account for ; and he wished any gentleman present to 

 give any information upon similar instances which may have come under 

 his observation, or for which he had any feasible theory. 



The Mystic Co., at Mystic, Conn., have an engine of fifty nominal horse 

 power uping a long slide-valve, and having a vertical bonnet, packed with 

 vulcanized rubber. This bonnet was found, after three' years use, to have 

 been so deteriorated in quality that the iron was like black-lead and could 

 be cut with a knife. Both the bonnet and steam-chest were removed, and 

 were replaced by others made of iron of a diiferent kind, yet the same 

 result followed after sufiicient use. There was a manifest connection 

 between the oil and the deterioration of the iron, for the latter was found 

 to occur near the oil cup, and at the back of the slide-valve. The oil gen- 

 erally used was pure sperm oil, but lard, coal and tallow oil have been used 

 and all with the same eflfect. The water used is the spring water of Mystic, 

 which is remarkably soft and deposits no scale. The steam is superheated 

 now about fifty degrees Fahrenheit above the point of generation, and the 

 pressure is about sisty pounds on the inch. The deterioration of the iron 

 does not depend upon the superheating of the steam, for at first the steam 

 used in this engine was not superheated. Further, the working parts — 

 the valve face and the cylinder — have not been affected. These are found 

 to be in good condition after five years' use. There were no observations 

 on the steam pipes, so that we cannot say whether it was due solely to the 

 steam, or solely to the oil, or to electric action. The steam-chest was four- 

 teen inches by thirty inches, and though the iron was changed, the bulk 

 continued the same, and it was deteriorated half an inch deep. The thick- 

 ness of the iron was one inch. 



Mr. Dibbin suggested that the action must be due solely to the oil, or 

 there would be corresponding action in the pipes. 



Mr. McCarty said the same is observed of iron resting in oil, or with oil 

 upon it. 



Mr. Howe. — To form plumbago, there must be more carbon added to the 

 iron. This it must get from the oil, as it could not get it from the steam ; 

 and the fact that the action is found near the oil shows such to be the case. 



Dr. Stevens alluded to the fact that oils are purified by the aid of sul- 

 phuric acid, which leaves some traces in the oil. This would act upon both 

 the iron of the bonnet and upon the sulphur of the packing. 



Mr.. Selleck gave an account of the manufacture of boiler plates, in which 

 he insisted upon the necessity of thorough care, as scrap or even soapstone 

 is liable to get among the billets or blooms, to be rolled or hammered. In 

 this way slag also gets worked up, and though the iron may seem all right 

 at the edges, towards the centre the plate will be weak and rotten. 



When the subject of the evening was called up, there were two or three 



