Another point of much importance, and particularly in Chimneys which are apt to smoke, is to form the throat of the Chimney properly, by carrying up the back and covings to a proper height. This, workmen are apt to neglect to do, probably on account of the difficulty they find in working where the opening of the canal of the Chimney is so much reduced.--But it is absolutely necessary that these walls should be carried up five or six inches at least above the upper part of the breast of the Chimney, or to that point where the wall which forms the front of the throat begins to rise perpendicularly. --If the workman has intelligence enough to avail himself of the opening which is formed in the back of the Fire-place to give a passage to the Chimney-sweeper, he will find little difficulty in finishing his work in a proper manner. In placing the plumb-line against the breast of the Chimney, in order to ascertain how far the new back is to be brought forward, great care must be taken to place it at the very top of the breast, where the canal of the Chimney BEGINS TO RISE PERPENDICULARLY; otherwise, when the plumb-line is placed too low, or against the slope of the breast, when the new back comes to be raised to its proper height, the throat of the Chimney will found to be too narrow. Sometimes, and indeed very often the top of the breast of a Chimney lies very high, or far above the fire (see the figures 13 and 14, where d shows the top of the breast of the Chimney); when this is the case it must be brought lower, otherwise the Chimney will be very apt to smoke.--So much has been said in the First Chapter of this Essay of the advantages to be derived from bringing the throat of a Chimney near to the burning fuel, that I do not think it necessary to enlarge on them in this place,-- taking it for granted that the utility and necessity of that arrangement have already been made sufficiently evident;-- but a few directions for workmen, to show them how the breast (and consequently the throat) of a Chimney can most readily be lowered, may not be superfluous.