Zinc, as a Covering for Buildings. 251 



This objection is based upon the fact that zinc melts at a low tem- 

 perature; and in case of fusion, leaves the wood work of the build- 

 ing unprotected. This objection is rather specious than real. Zinc 

 melts at the temperature of about 700° Fahr. or a little below red 

 heat. Whenever, therefore, the heat from adjacent buildings is any 

 thing less than that of redness, zinc would afford as complete pro- 

 tection as copper or iron. When the heat has reached the melting 

 point of zinc, which it seldom would do except in the most compact 

 parts of cities, very little confidence could be placed in the protec- 

 tion of iron or copper. The dry wood work of the roof, under a 

 covering of red hot iron, with air enough for combustion circulating 

 through openings and crevices, would soon be in flames ; and when 

 once in flames it would be extremely difficult to extinguish it by the 

 application of water. It would be applied with great disadvantage 

 to the under side of the roof, and almost to no purpose at all upon 

 the top. If therefore the heat, in any case, should become so in- 

 tense as to melt zinc, the probability of protection from iron or cop- 

 per will be but small. ^ 



Complete protection against fire is perhaps unattainable ; at least 

 we can never be sure that we have attained it. In the progress of 

 the arts, great improvements no doubt will be made in the mode of 

 defence against the attacks of this destroyer. I am not aware that the 

 following construction for a roof has ever been tried. For cheapness, 

 tightness, durability and resistance to fire, it seems to be well deserv- 

 ing the attention of builders. Let the rough boards of the roof, 

 (and the rougher the better,) be covered with a thick coating of 

 common lime mortar, — then lay down the ribs, if I may so call 

 them, for the zinc plates, — then cover the whole with zinc, according 

 to the most approved method of applying it. Such a roof would be 

 in no danger of leakage, unless the water accumulated upon it so as 

 to stand above the ribs, in which case no roof would be tight unless 

 it were calked or soldered throughout. This covering, if I am 

 rightly informed, would be nearly as cheap as slate — quite as cheap 

 as tin, cheaper than iron, and more than three times cheaper than 

 copper ; and would at the same time resist fire much better than 

 either of them. A heat that would melt down the copper and iron, 

 would, of course, melt the zinc, but would leave the mortar unin- 

 jured. The peculiar advantage of the mortar is, that it is infusible 

 except at a very high temperature, while the closeness with which 

 it adheres to the wood work is such as to exclude the air and thus 



