286 EIGHTH REPORT 1838. 



75. The box, No. 3, containing a similar set of specimens 

 with No. 2, has been deposited, by permission of the Dublin 

 and Kingstown Railway Company, in the hot-Avater cistern of 

 their baths at Salt Hill, in clear sea water, maintained con- 

 stantly at a temperature varying from 110° to 125° Fahr. The 

 object of this experiment is to determine the change of cor- 

 rosive action produced by increased temperature in sea water 

 containing but little combined air, and the differences of this 

 action on various kinds of iron. 



76. Van Beek and Dr. John Davy appear to be of opinion, 

 that sea water, after it has been boiled, is incapable of decom- 

 posing iron from containing no air 5 at the temperature of 125° 

 Fahr. decomposition is however most rapid, as the action of the 

 sea water on the iron cisterns of these baths demonstrate ; and 

 yet the water contains little air at that temperature. 



The results of my own experiments also show me, that after 

 all the air is expelled that can be from sea water by boiling, it 

 is still capable, at its boiling temperature, of decomposing iron, 

 and that with a rapidity as great as at ordinary temperatures, 

 however highly charged with air. In addition to which, there 

 is no longer any reason to doubt the fact, that under such cir- 

 cumstances the alkaline chlorides are in part decomposed by 

 the iron as M'ell as the other salts contained in sea water. 



77' Indeed Scoresby's experiments appear to prove that it is 

 impossible to deprive water, Avhether salt or fresh, of all its air, 

 by any amount of even alternate boiling and freezing. He found 

 that, on boiling briskly some sea water in a phial, and then 

 corking the latter and exposing it to cold, as the water froze 

 air bubbles began to appear moving upwards in the fluid, and 

 the ice produced was full of microscopic air bubbles. Hence 

 he concludes it probable, either that water is not entirely freed 

 from air by boiling, or that some of the water is decomposed 

 during the progress of the freezing process : of the latter there 

 is no likelihood. 



Boussingault also states that he found 16 per cent, of oxy- 

 gen in snow collected from the summit of Chimborazo in South 

 America. — {Annul, de Chi:n.) It is to be remarked, howevei", 

 that, as has been observed to be the case with lead and some 

 other metals, so iron seems to be corroded nmcli more rapidly 

 by air and distilled water at a high temperature, than by water 

 holding any alkaline or earthy salts in solution. The destruc- 

 tive effects of a small leakage of steam producing a trickle of 

 distilled water to steam boilers have often been observed by 

 engineers. 



78. The experiments of Dr. Faraday on the order of deposi- 



