2 REPORT—1843. 
sure, and to obtain the amount of this increment or decrement, the whole of 
the specimens previously exposed were, after examination and weighing, again 
immersed in their respective classes of sea or fresh water, and now, after a 
second period of exposure of 732 days, have been again taken up, examined, 
and weighed. 
284. Since the publication of the second Report these inquiries have also 
been extended to wrought iron and steel, of which between twenty and thirty 
varieties have been submitted to experiment. These have been immersed 
under conditions similar to the cast iron, vizi— 
1. In clear sea water, temp, 46° to 58° Fahr. 
2. In foul sea water, temp. same. 
3. In clear river water, temp. 32° to 68° Fahr. 
4. In foul river water, temp. 36° to 61° Fahr. 
and for the same period of 732 days. The results are given in the accompa- 
nying tables, so that we have determinations from two successive immersions of 
cast irons, and from one of wrought iron and steel. 
285. In addition, tabulated results will be found of experiments continued 
under similar conditions, and for an equally long period, upon wrought iron 
coated with zinc by the ordinary zinking process, or “galvanizing ” as it is called, 
and upon cast iron protected by the paint of powdered zinc (2nd Rep. 195). 
286. Besides the preceding, the results are given of an entirely separate 
set of experiments on cast iron, wrought iron and steel, exposed freely to the 
weather, and to all the atmospheric influences at an altitude of about fifty 
feet above the surface in the city of Dublin. It may be presumed that the 
accurate measures, thus for the first time obtained, of the actual metallic loss 
by rusting of a great variety of irons in the atmosphere, will not be looked 
upon as valueless by the engineer ; and accompanied as they are by the me- 
teorological registers kept at the Royal College of Surgeons, Dublin, for the 
time of experiment, will enable analogous results to be deduced for other 
localities where meteorological registers are also kept sufficiently comparable 
for all practical purposes; indeed the climate of Dublin may be viewed as a 
tolerably fair average of that of the British Islands, 
By a singular chance it happens that in the year 1840 (part of our period 
of experiment) the relative quantities of rain falling in Dublin and London 
are more than usually regular. There are on the average of six years— 
Days of no rain. Fair. No rain and fair. 
Tn !Dablinyeai\). bi. eo(1SQtineowed TeonbGrdt. lo oe » BOE 
In: London #61.) 6000220 bisve be ve)! TDi se ode sri 280 
And the average quantities of annual rain are— 
In Dublin 25°874 inches. 
In London 21°714: inches. 
July and August, which are warm months, are also generally weé months 
in Ireland. The actual quantities of rain which fell in Dublin and London 
in the two years of experiments were— 
1840. 1841, 
In Dublin . . 25°788 . . 28°882 
In London . . 18184 . . 27°372 
The temperatures were— 
1840. 1841. 
Daily Mean. Max. Min. Daily Mean. Max, Min, 
In Dublin . . 50°34 .. 85°0 . . 26°0 50°15 , . 78°0 . . 19°0 
In London. . 49°80 . . 83:0. . 21:2 ~ 604% ., 87:0... 149 
