Sun Spots

Sun Spots are dark regions, of great activity, occurring in the photosphere of the sun, and undergoing periodic alterations, the periods differing with different spots, but having a mean of about 11 years. These spots are of great interest on account of their agreement in time with certain magnetic phenomena on the Earth; the one grows greater or less as the other increases or diminishes. A typical sun spot consists of a black nucleus surrounded by a dark umbra, this in turn being bounded by a lighter penumbra, which seems of a lighter character and often sends out arms across the intervening umbra. Probably the spot is only carrying out the general movements of vapour in the photosphere, only on a much larger scale. Huge masses of vapour force their way downwards, carving a passage for themselves, and appear dark by absorbing the light fromt he hotter interior. So great are the disturbances in these spots, due to enormous variations in temperature and pressure, that they may be considered as capable of communicating their unsettled state to the Earth's magnetic condition. Spectrum analysis confirms the fact that great pressures occcur in these spots, enormous widening of certain lines being often found, while lines dlsplaced from their natural position in the spectrum show vlolent upward velocities of vapour.