Make a concrete of gravel or sand and Portland cement; or easier, of gravel, sand, coal-ashes, and coal-tar. Dig away the earth for 5 in., lay a bottom of pebbles as large as goose-eggs, ramming well down. Sweep off clean, and pay the surface with hot coal-tar, thinly; put on a coat of small er gravel previously dipped in hot tar, drained, and rolled in coal ashes with an intermixture of gravel. Roll it down as compactly as possible. Let the roller run slow, and let a boy follow it with a hoe to scrape all adherent gravel. Next, put on a coat of fine gravel or sand, coal-tar and some coal-ashes, to complete the surface. Roll again. This will take some weeks to harden, but. will shed water, and eventually form a very firm surface. Do not use too much tar, but only enough to make the ingredients cohere under pressure.