MECHANICS AND USEFUL ARTS. 103 



that steel mills are better adapted than stones. After being so converted, the 

 meal falls between the horizontal grindstones which reduce the meal into 

 flour. The great advantage consists in apportioning each of the grinding 

 surfaces to perform the portion of the grinding operations to which they are 

 best adapted, the steel for converting the grain into meal, and the stones the 

 meal into flour. 



CHEAP ROOFING FOR HOUSES. 



In all new settlements, whether timbered land or prairie, there is a difficulty 

 in procuring building materials, and the most difficult of all is a good mate- 

 rial for roofs, something as a substitute for shingles where shingles cannot be 

 easily obtained. Sawed boards are often substituted, but they form a very 

 unreliable protection ; and unless the board roofs are built very steep, they 

 are only a make-believe, and are withal quite liable to take sailing orders from 

 a " norther" as it sweeps unobstructed across the prairie. The best substi- 

 tute for shingles, probably, is a roof made of tarred paper ; and it has this 

 great advantage, that the work can be done by any common hands, and the 

 transportation is not heavy, or the material expensive. There is a tarred 

 paper sold at five cents a pound, one pound of which will cover a yard square, 

 or say half a cent a foot ; but we think this paper is rather too thin ; we 

 should prefer to have it twice the thickness, such as the thin, spongy straw 

 board paper used for light cheap boxes. It does not require to be strong, 

 and perhaps the cheap article alluded to will answer perfectly ; if so, a roof 

 can be made for one cent a foot. This paper comes in rolls, and may be laid 

 in courses up and down or across the roof, so that the edges are lapped, and 

 tacked with common No. 6 tacks, which would be very much improved by 

 using leather under the heads, as is often done in tacking carpets. The com- 

 position for covering a paper roof is made of the following ingredients : good 

 clean tar, 8 gallons ; Roman cement, 2 gallons ; rosin, 5 Ibs. ; tallow, 3 Ibs. ; 

 boil and stir, and thoroughly mix ah 1 together, and use hot, spreading it evenly, 

 in a thick coat, over the paper, which should be tacked upon thoroughly 

 seasoned boards kiln-dried are best well nailed up and down on lath 

 fastened to the rafters. The roof may be quite flat, rising only one foot in 

 twelve. In nailing on the paper, lap the courses as you would shingles, and 

 commence putting on the composition at the upper edge and work down, and 

 while the coating is still hot, let a hand follow and sift on sharp grit sand, 

 pressing it into the tar with a trowel or back of a shovel. When the first 

 coat is cool, go over with a second, and again with a third, and afterwards 

 once in five or six years, as long as your house stands, and you will have 

 a tight roof. 



In place of the Eoman cement, you may use very fine, very clean sand, 

 that is, silex in a state of impalpable powder. The paper is such as is used 

 under the copper in sheathing ships ; it is a soft spongy paper that soaks up 

 the tar, which penetrates through and glues it to the boards, and the sand 

 seems also to penetrate the substance of the paper, making it like stone. The 

 paper should be nailed on with short tacks with flat heads. The principal 

 objection to a paper and tar composition roof is its combustibility; but that 



