ACTION OF WATER ON IRON. 311 



and examine the reaction which may have taken place ; when 

 this has been done, it is purposed to give, in addition to the 

 foregoing data, the following information, with such other in 

 addition as may hereafter appear desirable. 



1st. The weight of each specimen when taken up after an 

 interval of twelve months, again after two years, and again, 

 perhaps, after a longer period. 



2nd. Loss of weight when cleared from adherent plumbago, 

 and weight of the latter when dry. 



3rd. Loss of weight per unit of surface. 

 4th. Loss of weight per unit of surface as referred to the 

 standard bar as unity. 



5th. Uniformity or otherwise of corrosion and its depth. 

 6th. Amount of water absorbed by the iron, if any. 

 7th. Chemical properties of the plumbago, e. g. if it ignite 

 spontaneously, &c. &c. 



8th. Physical properties of the iron if altered. 

 9th. Relative preservative effects of the various varnishes or 

 coverings, if any. 



As the giving the information under the second head above 

 will obviously render it possible that the reaction on the speci- 

 mens may be greater the second and subsequent years than it 

 would have been if the plumbago were not removed, means are 

 taken to compare the eflPects of water, &c. on iron in the same 

 times and circumstances as above, when the coat of plumbago 

 is periodically removed, and when it remains untouched for the 

 whole period of experiment. 



x2 



