ON RAILWAY BAR CORROSION. 105 
It is probable that the rate of this decrease will be more and more slow, 
and at a certain point of hardness reached by the condensation of the iron of 
the rail due to the rolling load, it will become and continue constant. 
2nd. The corrosion both in use and out of use appears also to decrease 
gradually upon the Kingstown line. The absolute corrosion in both cases is 
greater on the Dalkey line, owing to the increased dampness of the situation 
in which the rails were necessarily placed for experiment upon it, viz. in a 
shallow cutting with wet bottom. 
3rd. The difference between the corrosion in use and out of use, which 
exists throughout all the experiments, is also a constantly decreasing one. 
For purposes of general comparison, and of comparison with the corrosion 
of rails made of other makes or qualities of iron than those of the present 
experiments, it will be convenient to arrange the following table of the 
amounts of corrosion, both in and out of use, reduced to one square foot of 
corroded surface, and for a term of one year. 
The total exposed surface of the Dublin and Kingstown rail per lineal 
yard, is=2'88 square feet, but from this we have to deduct the top surface 
of the rail, which is rolled over in contact with the wheels, and which, being 
preserved bright, does not corrode, being 1°75 inch wide, which leaves a 
net surface of corrusion of 2°44 square feet per yard for the rails in use, and 
of 2°88 square feet per yard for the rails out of use as above. 
Taking the results of Table No. 4, therefore, we are enabled to deduce 
Table No. 5, which gives the corrosion in each case per square foot of sur- 
face of rail, and these results are then comparable with those of Table 15 of 
my Third Report on the Corrosion of Iron and Steel, &c., Transactions of 
British Association, and indeed comparable (by the aid of the standard bar 
as referred to in those reports) with all other results as to corrosion detailed 
therein, so that these experiments as to the corrosion of railway bars, may be 
hereafter extended or applied by others to rails rolled of any other make of 
iron whatever. 
TABLE No. 5. 

First Experiment,| Second Experiment, Third Experi 
Nature of action on the rail. |Dublin andKings-| Dublin and Kings- Da ik eka i 
town Railway. town Railway. alkey Railway. 


grs. avoir. grs. avoir. grs. avoir. 
Corrosion out of use 
per square foot of 213°38 76°00 96°18 
rail per annum.... 
Corrosion in use, or 
exposed to traffic per . , | ; 
square foot of rail LOA ieske 83°53 
per annum ...... 
aammrerences.......... 110°34 30°13 12°65 

Thus again the differences show a constantly descending series. 
If we extract from Table 15, Third Report on Iron, British Association, a 
few of the amounts of corrosion there given per square foot of surface, and 
reduce them to a period of one year, the foregoing corrosions will appear in 
all instances remarkably less. ; 
The results of Table 15 are, however, not sérictly comparable, as the iron 
there was exposed to the air and moisture of the City of Dublin, where the 
smoke and vapours, and excess of carbonic acid, close to the roofs and 
