PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 463 



the tar will be left. The union of the coal tar and the sand is 

 simply a niechauical union; all that he had seen used would not 

 answer in extreme cold weather, as it cracks. The best roofing 

 paint he found to be that made with oil, the same as painters pre- 

 pare, with the addition of a small quantity of beeswax, which 

 renders it elastic. This can be put on paper, layer after layer, 

 and will make a tolerably good roof. The addition of graphite to 

 this paint makes it still better. 



Mr. S. H. Maynard said: Roofing material, made of tar and 

 soapstone powder, mixed in equal proportions, has been put on 

 roofs at the Middlefield quarr^^ and they have required no repairs 

 for four years. There is also a building there covered with this 

 material eleven years ago, and is in good order now. If coal tar 

 could be had readily in the countr}', it would no doubt be the 

 best for covering barns. 



Dr. Thompson stated that he found Blake's roofing paint, mixed 

 Avith coal tar, a very desirable and lasting article. 



Mr. J. Wyatt Reid said that if there was any peculiar property 

 in powdered slate for roofing, it was due to its laminated, and not 

 to its angular qualities. 



Mr. Griffin presented samples of water-proof roofing, which 

 was made as follows: 1st. There is a heavy foundation of satura- 

 ted water-proof felt. 2d. A layer of composition. 3d. Another 

 layer of felt. 4th. Another layer of composition. 5th. Another 

 layer of felt. 



The whole is pressed into one solid impermeable fabric, and put 

 up in rolls fifty feet long by two feet wide, and when nailed upon 

 the roof-boards, is finally covered all over with a surface coating 

 of cement and sand, and thus is completed a roofing diflTcring from 

 all heretofore made. It unites the best kind of water-proof com- 

 position with the best water-proof fabric. It has been put on 

 buildings of all descriptions, and in all climates, and can be ap- 

 plied to steep or flat roofs, old or new, and by ordinary workmen, 

 at a trifling expense. The manner of combining the materials 

 employed in the construction of this roofing, by which it is made 

 into one firm, impermeable, uniform fabric, increases its durability, 

 while at the same time, being manufactured by machinery, on a 

 large scale, the cost is lessened. 



The Chairman made the following remarks on 



