The stone chimney is an advance and improvement upon the log chimney, but I doubt if it requires any more skill to build.
Chimney Foundation
Dig your foundation for your fireplace and chimney at least three feet deep; then fill the hole up with small cobblestones or broken bluestone until you have reached nearly the level of the ground; upon this you can begin to lay your hearth and chimney foundation. If you fail to dig this foundation the frost will work the ground under your chimney and the chimney will work with the ground, causing it either to upset or to tilt to one side or the other and spoil the looks of your house, even if it does not put your fireplace out of commission.
Stone Chimney
In laying up the stones for your chimney, remember that it makes no difference how rough and uneven it is upon the outside. The more uneven the outside is the more picturesque it will appear, but the smoother and more even the inside is the less will it collect soot and the less will be the danger of chimney fires. Lay your stones in mortar or cement. See that each stone fits firmly in the bed and does not rock and that it breaks joints with the other stone below it. By breaking joints I mean that the crack between the two stones on the upper tier should fit over the middle of the stone on the lower tier; this, with the aid of the cement, locks the stones and prevents any accidental cracks which may open from extending any further than the two stones between which it started. If, however, you do not break joints, a crack might run from the top to the bottom of the chimney causing it to fall apart. Above the fireplace make four walls to your chimney, as you did with your stick chimney ([Fig. 271]), and let the top of the chimney extend above the roof at least three feet; this will not only help the draught but it will also lessen the danger of fire.
XLIII
HEARTHSTONES AND FIREPLACES
In erecting the fireplace for your cabin the stone work should extend into the cabin itself, thus protecting the ends of the logs from the fire. The stone over the top of the fireplace (A, B, [Fig. 274]) rests upon two iron bars; these iron bars are necessary for safety because, although the stone A, B may bridge the fireplace successfully, the settling of the chimney or the heat of the fire is liable to crack the stone, in which case, unless it is supported by two flat iron bars, it will fall down and wreck your fireplace. The stone A, B in [Fig. 275], has been cracked for fifteen years but, as it rests upon the flat iron bars beneath, the crack does no harm.
