Write the construction of clinical thermometer.
Construction: It consists of a cylindrical bulb B which is filled with mercury. A capillary tube T of uniform and fine bore is attached to the bulb. Just above the bulb at point C the tube is made narrow and bent. Since the temperature of human body varies from 95°F to 110°F, the thermometer is calibrated in this temperature range. Each degree is divided into five small equal divisions. Besides, as the temperature of a healthy man is 98.4°F, so special bold or red mark is made on the surface of the thermometer at 98.4°F.