Thus by equation (18) of § II of the article Diffraction Of Light, the secondary disturbance is expressed by D' - D n 2 Tsin sin (nt - **kr**) D 47rb2 r _ D' - D irTsin O sin (nt - **kr**) (3)1 The preceding investigation is based upon the assumption that in passing from one medium to another the rigidity of the aether does not change.

The actual speed or rate of signalling is given approximately by the formula, S = 120/ (**KR**), where S is the number of words per minute, R the total resistance of the conductor in ohms, and K the total capacity in farads.

BY1Ahtuy) s'hc rlscpol Novibazar 4 Iv o V (i.?,b a - >{V I K **Kr** ftcs ?Piokuplye (Piro r; a yelopoly, 43 "fi es ova s i n ' 'M - ?..

In these expressions we are to replace p by ks/f, or rather, since the diffraction pattern is symmetrical, by **kr**/f, where r is the distance of any point in the focal plane from the centre of the system.

Its connexion with a is expressed by a =c4'/dr; so that TZ sin 05 e'(at - **kr**) 47b 2 where the factor e int is restored.

Retaining only the real part of (16), we find, as the result of a local application of force equal to DTZ cos nt (17), the disturbance expressed by TZ sin 4, cos(nt - **kr**) ?

According to (18), the effect of the force acting at dS parallel to OZ, and of amount equal to 2b2kD dS cos nt, will be a disturbance - dS sin cos (nt - **kr**) (20), regard being had to (12).

At B there is no displacement, but at K there is displacement towards B represented by **KR**, i.e.

P, foot; o, mouth (at the other end of the foot is seen the anus raised on a papilla); **kr**, oral fringe; br, the numerous ctenidia (branchial plumes); spreading beyond mentum which is porcellaneous, quite compact, and entirely covered by the tegmentum.

A2 y i-**Kr**) x2+B i,, ~~T) y+C2 y ~TT) 11 =0.

**Kr**., 1889), W.