<p>A fluorescent lamp with liquid mercury or low-temperature amalgam (12) is disclosed. At least one projecting bubble (61) is disposed on the wall of the luminous tube (9). An interconnection pipe (62) interconnecting the projecting bubble (61) and the luminous tube (9) is disposed between the projecting bubble (61) and the luminous tube (9). The interconnection pipe (62) is thinner than the projecting bubble (61). A thermal resistance is produced between the tube (9) and the projecting bubble (61). The projecting bubble (61) is thicker than the interconnection pipe (62) so that it is contributed to heat dissipation with a larger surface area. Accordingly, the temperature inside the projecting bubble (61) can be adjusted to a desired working temperature of liquid mercury or low-temperature amalgam (12), so that a stable desired vapor-pressure of mercury is obtained inside the cavity of the luminous tube(9).</p>
