316 On Zine 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. 
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 “poof perfectly tight,’ and 
this is proved he says “ by numerous certificates that place the sub- 
ject beyond all reasonable doubt. A zine 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. 1 think I can point out between seventy and one 
hundred buildings, to my 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- 
tion, 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 @aterial. 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 | Lee in making a zine roof perfectly tight? Has 
Messrs. Crocker and Brother’s zinc not come to the New York 
