514 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



and injury from dirt, I believe we should find that the common pavement 

 costs ten times more than the best iron pavement. 



But if the best and most agreeable paving were to cost double or treble; 

 if, instead of $1,200,000 per year, which we have in some years paid for 

 paving and cleaning, we were to pay three millions, and be free from dirt, 

 I think the citizens would choose the decent system, and no more desire 

 to resume the indecent one, than they desire to be relieved from the Crotou 

 water and the cost of it, or the sewers and their cost. 



But if the citizens generally, of all conditions, did wish to endure the 

 present nuisances, rather than pay the taxes necessary to maintain a 

 system accordant with taste and science, it would be the more incumbent 

 on a liberal scientific association to show the desirableness of the better 

 system. It may be the policy of politicians to tell the public only what 

 the public already knows, or is prepared to believe; but men of science, 

 who belong to the liberal professions, must not seek popularity by such 

 means. This I say for the admonition of those who are disinclined to agi- 

 tate improvements that are not likely to come into use within a short time. 



Not only in streets, but in suburban thoroughfares, and in ail roads of 

 great traffic, would this means of surfacing be applicable. Cast iron would 

 be profitable where the traffic exceeds a certain amount, easily found by 

 calculation. On roads of less traffic, but still considerable, lava would be 

 profitable, as I think. But I do not know the cost of making it; the heat 

 required; the distance from which the materials would have to be brought; 

 these are points upon which I ask for information. 



After which the regular subject for the evening, " Harbor Defences, and 

 the Use of Iron-clad Vessels," was taken up, when the Chairman said: 



It will be remembered that we had this subject once before under discus- 

 sion last winter, but since then some new experiments have been made at 

 the South, and the civilized world is anxiously waiting the result of the 

 recent trial at Charleston. As this is the third practical test of iron clad 

 vessels, and some important facts in naval warfare have been determined, 

 the subject has been again selected for discussion. 



Mr. Dibben. — The accounts of the late trial at Charleston are so very 

 meager, and so little that is definite known, that we cannot enlarge very 

 much on our previous discussion, and all that I can say I fear will be but 

 a repetition of what has been said before. There is this difiPerence, how- 

 ever, in the late fight, that it was not iron-clads against iron-clads, but 

 forts against iron-clads, and the iron-clads stood it well; from what we 

 have heard, these iron-clads have stood all the battering the forts were 

 capable of giving, without incurring any serious damage. Whether they 

 tried to remove the obstructions in Charleston harbor does not appear; but 

 from what we know we can conclude that the barring up of the entrance 

 to this city at the Narrows, will stop all the iron-clads in the world. We 

 have penetrated seven and eight inches of iron through and through, at a 

 little less distance than this battle was fought. The English and French 

 iron-clads have plates of from four to five inches thick; every shot from our 

 rifle guns would go through these plates, at 400 and 500 yards. I do not 

 think that all the iron-clads in the world would undertake to do what these 

 seven monitors did, to expose them to a fire of 300 heavy guns for over 



