316 On Zinc Roofing. 



mer paper, and then proceed to give the details of my experiments, 

 and let others who may be disposed to read the article draw their 

 own conclusions. 



Prof. Caswell commences the argument in his paper on the three 

 following subjects, supposed to have been the divisions of my paper 

 in the Mechanics' Magazine. 



1 . Difficulty of making the roof tight. 



2. Deterioration of the water which falls from it. 



3. Comparatively small resistance which it offers to the progress 

 of fire. 



My own division, however, is quite another thing : it is the fol- 

 lowing. Zinc is objectionable, (as a roofing,) First, from the great 

 expansive power of the metal. Secondly, its brittleness. Thirdly, 

 it deteriorates the water. 



As Prof. C. has embraced my threefold division under two heads, 

 namely, tightness of roofs and deterioration of the water, I shall 

 make a few remarks on each of these. As his third division has no 

 place in the original paper in question, it need absorb no time in this. 



On the difficulty of making zinc roofs tight Prof. C. states, " There 

 is no practical difficulty in making a zinc roof perfectly tight" and 

 this is proved he says " by numerous certificates that place the sub- 

 ject beyond all reasonable doubt. A zinc roof may as easily be 

 made tight as any other. There may be sheet zinc in the market 

 of a bad quality, but none need be deceived on this point, since noth- 

 ing is easier than to test its flexibility." 



This is, it must be confessed, a pretty summary way of disposing 

 of so important a matter. There is probably no place in the United 

 States, where the experiment of zinc roofing has been so extensively 

 tried as in this city. I think I can point out between seventy and one 

 hundred buildings, to ray personal knowledge, that have been covered 

 with zinc, and in a very considerable portion of them it has been re- 

 moved, and its place supplied by copper, tin, or slate ; and those roofs 

 that still remain, covered by zinc, I have ascertained by careful inves- 

 tigation, are more expensive to keep in repair than any other roofs 

 whatever ; and furthermore, I would say, that zinc is now almost en- 

 tirely out of use in this city as a roofing material. Let me ask my 

 friend Caswell, why most of our New York builders, as well as the 

 proprietors of buildings, have abandoned the use of zinc, if there be 

 no practical difficulty in making a zinc roof perfectly tight? Has 

 Messrs. Crocker and Brother's zinc not come to the New York 



