What shall we do with crevices and cracks? At first, I hoped that narrow chinks might be ignored, on the principle that easy passages of air through an ample screen would virtually stop off currents through narrow spaces. In this I have been disappointed, as, in some cases, a chink, though apparently narrow, has proved too accommodating to the passage of air, and a more ready channel than the interstices of flannel. My rule now would be to close or guard with filtering material every place where the door comes into contact with its frame.
The plan I have adopted with the doors of several cupboards and closets is this—to put strips of cotton velvet wherever the door comes into contact with its framework. On the side where the hinges are, the velvet is glued and sprigged to the edge of the door; on the other side and the top the velvet is fixed to the rebate against which the door presses. If the door belong to a closet, and the bottom is not in close contact with the floor, a small piece of flannel or cloth may be fixed along the inner side of the bottom of the door, so as to form a curtain which closes the gap, and filters any air that passes through.
Such, then, are the principles which may guide us to a victory over dust, and such are some of the details whereby we may work out a method by which the victory is to be won. Do not suppose that I claim to have completely conquered the enemy; but a beginning has been made, a beginning definite enough and assured enough to encourage others, and especially architects, to study the question and to make trials. If they will but work with determination to conquer, they may confer upon the community a most welcome amelioration of some of the smaller miseries we have to submit to.
And now let me venture to tell you what I should do were I to construct an office in the center of a town. I should begin with the fireplace. Let it be constructed on the principles I have been teaching for the last ten years, and which were brought to a focus in my lecture at the Royal Institution in 1866—principles which are at last influencing the construction of fire-grates throughout the kingdom. Shortly stated, they are:
1. The back and sides of the fireplace to be fire-brick, built solid.
2. The depth of grate from front to back never to be less than nine inches.
3. The back to lean over the fire, not to lean away from it.
4. The front bars to be vertical and thin, not horizontal and thick.
5. The ash-place under the grid to be made into a closed hot chamber by a movable shield, named an "economizer."
The effects of this construction are:
