100 REPORT—1849. 
There ist aerefore on this second experiment a distinct corroboration of 
the result of the former Table No. 1, viz. that there is a real diminution of 
corrosion in the rails, due to trafic. The absolute amount of difference is 
less however in this second experiment than in the first. By Table No 1 it ap- 
pears that the ratio of the corrosion of the unused, to that of the used rails, was 
as 15°30 : 6:06; but in the present case we find the ratio to be as 83°12 : 48°13, 
or as 1 to 2°5 in the former, and : 
1 to 1°7 in the latter. 
‘Hence the difference is a decreasing one, the causes of which we shall again 
refer to. r 
The whole three sets of rails in this experiment were weighed carefully 
before being cleaned just when removed from the line, and without any ad- 
herent rust or other matter being shaken off from them, and, as already stated, 
again weighed after having been brushed and cleaned. The difference 
showed the amount of adherent’ owide attached as a scale to the uncoated 
rails, and of varnish coating on the others. 
The weight of detached matter was as follows :-— 
No. 1. Uncoated, not travelled over...... 5,250 grs. 
No. 2. Uncoated, exposed to traffic...... 1,313 
No. 3. Coated, and exposed to traffic .... 11,375 
consisting all of coal-tar and dust. 
From this it is apparent that the coat of adherent rust upon the unused 
rails was on equal surfaces to that on the rails exposed to traffic, as 52°5 to 
13°1, or that the adherent rust on the unused rails is nearly four times as 
thick as on the rails exposed to traffic, proving that the oxide formed on the 
latter is constantly shaken off by the vibration of passing trains. 
It is now desirable to give the amount of traffic which passed over the rails 
during the period of the last experiment, viz.— 
Traffic in tons passed over the Dublin and Kingstown Railway between 
18th October 1842 and 18th October 1844, per T. F. Bergin, Esq. 
2? 
> 
Tons. 
4,041,075 passengers at 15 per ton .........+-- - 269,405 
59,243 engines at 15 tons each............++- 888,645 
437,791 coaches, average 3} tons each ........ 1,532,268 
Total in both directions ............ 2,690,318 
The traffic being precisely equal up and down, and the passengers Tons. 
very nearly so, say for gross traffic over experimental rails one- 
half the aboves=. (05 9220) 2 Oa vile sae ies ere eee be oie 1,345,159 
To which add for ballast brought over experimental rails during 
the two years, and for luggage .......... amigo iat Ghisip-aten tenses 
Total load transferred over experimental rails= ...... 1,355,159 
or 677,5794 tons per annum. Only half this, however=677,5795 tons in 
the two years, or $38,7892 tons per annum, traversed each length of ex- 
perimental rails. 
This latter weight produced in the two years an absolute abrasion on 30 
yards of rail of 47,687 grs. avoir. or of 23,844 grs. per annum, which is 
nearly 795 grs. abraded per yard per annum, or an abrasion of iron amounting 
to ‘00235 gr. per ton per yard, or 1760 x 00235=4'136 gr. per ton per mile. 
The absolute abrasion is therefore less in this second experiment than in 
the first, in the ratio of 4 to 9°5 in round numbers, proving that the upper 
surface of the rails gradually alters in texture, and gets hardened by the 
rolling over it of the loads, so as to be less and less abraded in proportion 
to the load passed. This fact, however, can only apply to cases where the 

