If it is desired to attach the thread to its supports merely by shellac, this is practically all that needs to be done. The supports should resemble large pins. The upper support will be a brass wire in most cases, and will require to be filed away as shown in the sketch (Fig. 71). It is then coated with shellac by heating and rubbing upon the shellac. As previously noted, the shellac must not be overheated. The thread is cut off below the lower slip of paper, and the upper support being conveniently laid in a horizontal position on another dead-black surface, the thread is carried to it and laid as designed against the shellac, which is now cold. When the thread is in place, a soldering iron is put against the brass wire, and the shellac gradually melted till it closes over the thread. Fig. 71. The iron is then withdrawn and the thread pulled away from the point for one-twentieth of an inch or less. This ensures that the thread makes proper contact with the cement, and also that it is free from kinks; of course, it must leave the cement in the proper direction. A similar process is next carried out with respect to the lower attachment, and the ends of the thread are neatly trimmed off. Both ends of the thread being secured, the next step is to transfer the upper support to a clip stand, the suspended parts being held by hand, so that the weight comes on the thread very gradually. In this way it will be easily seen whether the thread is bent where it enters the shellac, and should this be the case, a hot iron must be brought up to the shellac and the error rectified. When both the support and the suspended parts are brought nearly to the required bearing, the hot iron is held for a moment close up to each attachment, the hand being held close below but not touching the suspended parts, and both attachments are allowed to straighten themselves out naturally. These details may appear tiresome, and so they are when written out at length, but the time occupied in carrying them out is very short, and quartz threads break easily, unless the pull upon them is accurately in the direction of their length at all points. In the event of its being decided to attach the thread by soldering, the process is rather more expensive in time, but not otherwise more troublesome. Fig. 72. Fig. 73.