(b) In breaking a glass tube, e.g., a combustion-tube, a small scratch is made with a file at the required place. At each side of this scratch, and about 1-2 mm. away from it, a small roll of wet blotting-paper is laid round the tube. The free space between is then heated all round over a Bunsen burner, or better still, over a small blowpipe-flame. A clean and even fracture is thus obtained, exactly between the two rolls, without dropping water on the hot glass. The rolls are made by cutting two strips of filter-paper, sufficiently large to form rolls 1-2 mm. high, and 2-4 cm. wide. The strips are folded once, lengthways, laid on the table, moistened, flattened out, and then wrapped on to the tube, so that the fold lies nearest the file-scratch, and fold lies accurately upon fold in the successive layers. The thickness of the rolls, and their distance apart, has, of course, to be varied, according to the diameter of the tubes.
Equally good results are obtained with the thinnest teat-tubes, the thickest combustion-tubes, beakers, flasks, and glass bell-jars. In those cases, where the sides are slanting, as, for instance, with funnels, an obvious alteration in the construction of the paper rolls need only be carried out. (Analyst.)