Preston—Radiation Phenomena in a Strong Magnetic Field. 391 
normal triplet. For example, if the corresponding lines differ in phase at their 
centres by half a period, then a sextet would result ; and if the middle lines only 
differ in phase, a doublet or a weak-middled quartet would result. In fact, all the 
appearances observed so far might result in this manner, and, if so, additional light 
will be thrown on the structure of the spectral lines. It is just possible, however, 
that the complexity of structure observed by Michelson may itself be due to 
intermittent reversal, that is, absorption. 
