When these two forms of joint have been mastered, a T piece will present but little difficulty. It is made in three stages as shown in Fig. 5, and the procedure is similar to that used in joining a large and small tube. Care should be taken to avoid softening the top of the "T" too much, or the glass will bend and distort the finished work; although a slight bend can be rectified by re-heating and bending back. Local re-heating is often useful in giving the joint its final shape. An exhaustion branch is often made by a totally different method. This method is shown by _g_, _h_, and _i_, Fig. 5; _g_ is the tube on which the branch is to be made. The end of a rod of similar glass should be heated until a mass of thoroughly liquid glass has collected, as shown, and at the same time a spot should be heated on that part of the tube where it is desired to make the branch. The mass of hot glass on the rod is now brought in contact with the heated spot on the tube and expanded by blowing as shown by _h_. The air pressure in the tube is still maintained while the rod is drawn away as shown by _i_. This will give a hollow branch which may be cut off at any desired point, and is then ready for connection to the vacuum pump. If the rod used is of a dissimilar glass, the branch should be blown much thinner. Such a branch will often serve as a useful basis for joining two tubes of different composition, as the ordinary type of branch is more liable to crack when made with two glasses having different coefficients of expansion. _Blowing Bulbs._--A bulb may be blown on a closed tube such as that shown by _c_, Fig. 5, by rotating it in the blowpipe flame until the end is softened, removing it from the flame and blowing cautiously. It is desirable to continue the rotation during blowing. In the case of a very small tube, it is sufficient to melt the end without previous sealing, rotate it in the flame until enough glass has collected, remove from the flame and blow while keeping the tube in rotation. _Thermometer Bulbs._--If the thermometer is to be filled with mercury, it is desirable to use a rubber bulb for blowing, as moisture is liable to condense inside the tube when the mouth is used, and this moisture will cause the mercury thread to break. In any case, a slight pressure should be maintained inside the thermometer tube while it is in the flame; otherwise the fine capillary tube will close and it will be very difficult to expand the heated glass into a bulb.