BAS REPORT—1840. 
sible, for a future and final report, and confine the present to 
the results and their modifying conditions which have already 
been obtained, and are of practical value and importance to the 
civil engineer, the iron founder, or the iron-ship builder. 
142. I proceed, then, to state the general nature of the ac- 
companying tabulated results of experiment. The first five 
tables contain the data and results of the chemical or corroding 
action of sea and fresh water on cast and wrought iron under 
five several conditions of experiment, continued during a period 
of between a year and thirteen months. 
It will be seen that these five first tables, so co-ordinate with 
each other as to form one connected and comparable whole, by — 
which have been determined the relative rates of corrosion, and 
the absolute amount thereof, for eighty-five several sorts of cast 
and wrought iron, under each of the following conditions, viz. 
1. In clear sea water, at temp. 46° to 58° Fahr. 
TI. In foul sea water, ai 46°. Din 
III. In clear sea water, a 1 a a 
IV. In foul river water, ,, 36%, 5 selene 
V. In clear river water, 5, a 3 aati 
143. During the period in which the several sets of speci- | 
mens have been immersed, the five waters acting on them have 
been examined as to their physical and chemical properties. 
144. The water of No. 1, that of Kingstown Harbour, con-— 
tains, in a cubic foot, 12661 grains of solid matter, which — 
analysed with precaution in the usual manner, had the follow-_ 
ing constitution reduced to per cent. : 
Chioride sodium... .. se + isi ney F832 
Chloride magnesium . - + + + 10°79 
Bromide magnesium - - + = - 0°60 
Sulphate lime. . +. -(* s+ «+ + 4:87 
Sulphate magnesia. - + + + = 5°30 
Ganhatiate UuMeis..)ena>Sastasdor seed aaa 
Organic matter. - + + + 8 + 5:27 
The Arc acd om’ dstaleante cule a acu 
Grads 
100°00 
I could not detect any chloride of potassium or carbonate 
iron, said to be occasionally present in minute quantity in sea 
water. The amount of organic matter is very variable. It 
therefore appears not to differ much in composition from the 
waters of the British Channel, but considerably from those of 
the Mediterranean and the Atlantic Ocean, as given in the best 
