1082 Experiments and Papers, [No. 144. 



iron exposed to fresh attacks from the combined action of air and 

 water. As surely and as rapidly as are the iron tanks for containing 

 fresh water in men of war rendered useless by a similar operation, so 

 will the hulls of iron vessels be corroded and destroyed, whilst the 

 same mechanical means of protection which externally acts injuriously, 

 forming a bed favorable for the attachment of marine vermin, would, 

 applied internally, be the very best remedy that could be devised for pre- 

 venting the extensive oxydization of the iron in this situation. I allude 

 of course to the layers of coal tar, or otherwise bituminous compounds 

 with which it is usual at present to overlay the bottoms of iron vessels. 

 As general opinion, however, appears to be in favor of some external 

 covering for the iron, I know of none better suited to the purpose, 

 than a medicated application long in use among the Persians and 

 Arabs to protect the bottoms of their dows and other vessels from the 

 adhesion, and consequent depredations of marine animals, and which 

 appears to owe its protective power to the character of its principal 

 ingredient — aloes, which either from its bitterness, or being a positive 

 poison to such animals, completely prevents their adhesion ; and as this 

 in the case of iron vessels is a desideratum, a trial of it might be made, 

 for I see no reason why the application should not operate equally 

 beneficial in the one case as the other. The formula for its preparation, 

 according to a recent publication under the head '* Aloes," is as follows : 

 One ounce of aloes mixed with turpentine, tallow and white lead, is 

 sufficient for covering two feet, and it requires about twelve pounds for 

 a vessel of fifty tons burden. As a simple modification of this, I 

 should recommend, that to the common red lead paint usually applied 

 to the bottoms of iron vessels, such a quantity of aloes be added, as to 

 make it correspond as nearly as possible with the composition used by 

 the Arabs. One hundred weight of aloes, would be about sufficient for 

 a vessel of 500 tons burden. 



With respect to iron tanks for containing fresh water, here perhaps 

 the electro-galvanic influence might be beneficially employed, although 

 one probable result might be the putrefaction of the water, which in 

 common unprotected tanks, remains for a considerable length of time 

 both sweet and wholesome. Its admixture with the very visible parti- 

 cles of detached oxide of iron, is the only thing complained of by the 

 sailors, but as this is in some measure conducive to their health, a 





