248 Zinc, as a Covering for Buildings. 
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Arr. V.—On Zinc, as a Covering for Buildings ; ina letter from 
Prof. A. Caswrxz to Messrs. Crocker, Brothers & Co. 
You some time ago requested me to examine an article on Zine, 
as a roofing material, published by Dr. Gale of New York, in alate 
number of the Mechanics’ Magazine. I regret that it has not been 
in my power to give your request earlier attention. 
The remarks of Dr. G., which were copied by several papers at 
the time, were fitted, in your opinion, to prejudice the public mind 
unjustly upon a subject of great importance. He discourages the 
use of zine as a roofing material, upon several distinct accounts, the 
principal of which are the following. 
1. The difficulty of making the roof tight. 
2. ‘The deterioration of the water which falls from it. 
3. The comparatively small resistance which it offers to the pro- 
gress of fire. rs 
1. As to the first of these objections, the brittleness of the metal 
~ and its great expansion from heat are adduced, to show that a roof 
cannot be made sufficiently tight. Zinc in the unwrought state 18 
well known to be very brittle, and there may be in the market rolled 
or sheet zinc of a bad quality. But no one need be deceived on this 
point, since nothing is easier than to test its flexibility. Sheet zinc — 
which will bear to be doubled and hammered down without any ap- 
pearance of fracture in the bend, may be used as a covering for 
buildings, without the least fear of leakage. Such is the fact with 
regard to sheet zinc which I have examined from your manufactory 
and such, 1 am assured, is the fact with regard to foreign zinc from 
the best manufactories. But any detailed examination of the brit- 
tleness and expansion of zinc, so far as this question is concerned, 18 
entirely obviated by the well ascertained fact, that there is no prac- 
tical difficulty in making a zine roof perfectly tight. ‘The numet- 
ous certificates which you have submitted to my examination, from 
most respectable gentlemen, who have made the experiment, place 
the subject beyond all reasonable doubt. A zinc roof may as easily 
be made tight as any other whatever. 
2. The second objection respects the deterioration of the water 
which falls from the roof. This consideration is particularly impor- 
tant to all those who are in the habit of using cistern water for culi- 
nary and other domestic purposes. 
