A bulb is blown between two tubes by the method given on page 22, the larger tube is then cut off and the small piece of tube introduced into the bulb after having been shaped as shown in by _b_, Fig. 9. The opening in the bulb is sealed as shown by _b1_. The sealed part is now heated and the bulb inclined downwards until the inner tube comes in contact with the seal and is fused in position. This operation requires some practice in order to prevent the inner tube either falling through the soft glass or becoming unsymmetrical. The end of the bulb, where the inner tube comes in contact with it, is now perforated by heating and blowing, thus giving the form shown by _b2_, and the outer tube is joined on. The finished spray arrester is shown by _b3_. Practice alone will give the power to produce a symmetrical and stable piece of work. _Two Forms of Filter Pump._--That illustrated by _d_, Fig. 9, is made by the method explained under "An Air Trap on a Barometer Tube." That illustrated by _c_ is made by the method explained under "A Spray Arrester." No new manipulation is involved, and the construction should be clear from a study of the drawings. _Multiple and Branched Internal Seals._--A fuller consideration of these will be found on page 39, but one general principle may well be borne in mind; that, as far as is possible, a tube having both ends fastened inside another tube or bulb should be curved or have a spiral or bulb at some point in its length, otherwise any expansion or contraction will put great strain on the joints. _Sprays._--A spray which is easy to make, easy to adjust, and easy to clean after use is shown by _e_, Fig. 9. The opening on the top of the bulb is made by melting on a bead of glass, expanding, bursting, and fusing the ragged edges. The two branches which form the spray producing junction are made by the method used for an exhaustion branch and described on page 18. A spray which can be introduced through the neck of a bottle is shown by _h_, Fig. 9. The various stages in making this are illustrated by _f_, and _g_. If the inner tube is made by drawing out from a larger piece of glass so that two supporting pieces are left on each side of the place where it is intended to make the final bend, that bend can be made in a flat-flame gas burner without causing the inner tube to come in contact with the walls of the outer tube. Care must be taken when joining on the side piece that the inner tube is not heated enough to fuse it. The small hole in the side of the outer tube is produced by heating and bursting.