By supposing the retardation to vary uniformly and continuously we, fall upon the case of an ordinary prism: but there;, is then no diffraction spectrum in the usual sense.

The rate of diminution of amplitude expressed by the coefficient a in the index of the exponential is here greater than the coefficient b expressing the retardation of phase by a small term depending on the emissivity h.

If the retardation be too little, the overlapping of the processions is incomplete, so that besides the procession of half period there are residues of the original processions of full period.

After a very short interval of time, the length of which depends on the inductive retardation of the cable, the condensers corresponding to C 1 and C3 at the other end begin to be charged from the cable, and since the charge of C3 passes through the receiving instrument I or G the signal is recorded.

when the secondary wave of least retardation is unobstructed, or when a ray passes through the point under consideration.