PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 433 



Roofing Material. 



The discussion of this subject was opened by the Chairman. 

 He alluded to the importance of the subject, and the meagre infor- 

 mation in relation to it to be foiwid in the books on building mate- 

 rials. 



Dr. D, D. Parmelee remarked that much of the difficulty in 

 obtaining a permanent roofing material lay in the fact that what 

 would answer in one locality would not in another. A tin roof 

 that might suit this locality could not be used in Boston. 



Mr. Robinson exhibited specimens of his roofing cloth. He 

 said it was made of calendered paper saturated with coal tar. On 

 one sheet of paper is spread a layer of bituminous composition 

 after which the sheet is compressed between two calender rollers 

 by which the composition is made to adhere firmly to the paper. 

 Then again another sheet of paper and a layer of the composition, 

 and passed through the rollers which holds the fabric together 

 and makes one solid sheet- The number of sheets of paper varies 

 according to the quality of the roofing. The composition is pro- 

 tected from atmospheric influence by the felt which is laid on the 

 top. The composition protects the fabric and the fabric protects 

 the composition. The paper felt costs about six cents a pound. 

 There are objections to all kinds of woven fabric in roofing mate- 

 rial, as their woven texture will be worn through; but felt is not 

 acted on in this v^ny. The stock that this felt is made of is from 

 the waste of the mills, old ropes, &c.,' sometimes woolen rags are 

 used in small quantities, which serve only to make the fabric a 

 little more open. The best composition for roofing is worthy of 

 much consideration. There have been over two acres of this 

 roofing put on buildings in Kansas within the last tv/o months. 

 He claimed that his method was the best form of putting the roof- 

 ing together. At about 150 degrees the tar between the layers 

 would become soft at the edges, but not sufficient to make it run. 

 This style of roofing has been made by machinery for two years. 

 He had seen pieces of red hot coals thrown on this roofing, but 

 they failed to ignite it. It seems to be as good a protection 

 against fire as any ordinary roofing except tin or slate. The rolls 

 used for uniting the sheets are twenty-two inches wide and fifty 

 feet long. All his experiments with woven fabrics have been 

 failures. 



Adjourned. 



[Am. L\st.] BB 



