Tightly strain across an old drawing-board, by means of tacks slightly driven, a piece of cotton tolerably good quality, but do not damp it, except with paste, as hereafter mentioned. Work the last in well with a painter's brush that has not been used for any other purpose. It is advisable to soak the brush, before using, for a few hours in cold water, so as, by expansion of the handle and constriction of the cordage, to tighten the hairs, and prevent them coming out with the paste. Paste also the back of the tracing, and, obtaining the assistance of another person, hold it by the corners over the strained fabric, allowing it to sag well, and lower it gently until the middle of the tracing first come into contact with the calico, after which gently and simultaneously lay down each corner. The tracing may now be gently dabbed with a clean cloth, commencing at the middle, and working out the blisters to the edge. A needle may sometimes be used with advantage to puncture small holes and set free the air in some of the obstinate blisters; but do not trouble to remove them all, as the smaller ones will quite disappear in drying. Do not rub the tracing whilst wet without the intervention of a sheet of large thin lining paper, such as is used for lining walls. Allow the tracing to dry gradually on the board without fire heat, and do not remove it until thoroughly dry. Draw on the scale before mounting, so that it may, by contracting and expanding with the drawing, be always true. The tracing, when mounted, presents a better surface for coloring than before. The board should be cleaned before using.