1885.] 



Note on an Experiment by Chladni. 



249 



on examination fonnd that "the spores from both are of the same 

 size, all being, I believe, macrospores." I have since examined a 

 number of commercial specimens of lycopodium, but have not' met 

 with any containing microspores. 



The powder of sublimed sulphur was also dusted over the plate, 

 when on sounding the note E, fig. 1 was beautifully produced, the 

 nodal lines being well defined, and not much coarser than with sand ; 

 but the flowers on the vibrating centres were much more diffused, 

 shading off into cloudiness much more than with lycopodium. The 

 sulphur also was not so active. Figs. 3 and 4 are attempts to repre- 

 sent the action of sulphur alone. 



After a layer of iron filings had been sifted on the plate, a layer of 

 sand was added, when the finer particles of iron did not escape to the 

 vibrating centres, they being apparently imprisoned by the sand. 



Flowers of sulphur being dusted on the plate, and then lycopodium, 

 a certain amount of winnowing goes on under the influence of vibra- 

 tion, the sulphur for the most part going to the nodes, and the lyco- 

 podium to the centres (fig. 5). When either of these or a similar light 

 powder is used alone, the slight adhesion of the powder to the plate 

 on and about the nodal lines is sufficient to retain it there, while the 

 looser upper particles are swept upon the centres. 



The cyclonic air currents are well shown by flowers of sulphur, 

 when the plate is thrown into its greatest amplitude of vibration by 

 sounding either of the two lowest notes, D in the bass clef, and Ab 

 below the lines of the treble clef, the figures being the well known 

 crosses which terminate, one in the centre of the edges, and the other 

 at the angles of the plate. In either case there are but four vibrat- 

 ing centres, and the powder occupies a considerable space on each, 

 and is whirled round in numerous eddies, which can be distinctly 

 followed by the eye, showing how the separate heaps of lycopodium. 

 are formed when this powder is used instead of sulphur, which does 

 not collect in heaps, bat in curved parallel ripples, convex towards 

 the fixed centre of the plate. 



The brass plate thus fixed yields but a limited number of figures. 

 By using plates of various material and form, such as bell metal 

 bronze, white metal, glass, &c, in squares, parallelograms, ovals, &c, 

 fixed at any point by means of Chladni's clamp, an endless variety of 

 forms may be obtained. In the following figures the small white 

 circle shows where the plate was clamped. 



The presence of flowers of sulphur gives a softened effect to the 

 figure, and converts the sharp angles formed by sand alone into grace- 

 ful curves. Pig. 6 shows the effect of sulphur and lycopodium com- 

 bined ; fig. 7 of sand and lycopodinm, where the finer powder collects 

 in heaps. In the more complicated figures which follow it is remark- 

 able to note the precision with which the lycopodium becomes sepa- 



T 2 



