National Geographic : 1943 Jan
Glass "Goes to Town" It Takes More Than a Hundred Operations to Make the Familiar Instrument The hot, taffylike gob is anchored at its thick end in a draw-up machine and the blowpipe attached to a cable. This electric draw machine pulls the glass 150 feet or more high and forms the tube for the thermometer maker (upper left). As drawing progresses the tubing is measured with calipers (upper right). Tubing is cut into six-foot lengths (lower left). Held in a circular rack, thermometers are immersed in an electrically heated bath to locate position of scale before graduating (lower right).