RESEARCHES AND EXPERIMENTS. 



727 



graphs of a person were taken at different 

 times, their composite would possess those in 

 which a single photograph is deficient. The 

 last use of the process proposed by Mr. Galton 

 is one suggested by his own special study 

 that of heredity. "A composite," he writes, 

 " of all the brothers and sisters in a large fam- 

 ily would be an approximation to what the 

 average of the produce would probably be if 

 the family were indefinitely increased in num- 

 ber ; but the approximation would be closer if 

 we also took into consideration those of the 

 cousins who inherited the family likeness. As 

 regards the parentage," he adds, " it is by no 

 means sufficient to take a composite of the two 

 parents ; the four grandparents and the uncles 

 and aunts on both sides should be included." 

 If these two composite portraits of the parent- 

 age on the one hand, and of the produce (de- 

 scendants) on the other be compared, they 

 will show the hereditary transmission of fea- 

 tures. 



An Enemy of the Coffee-Plant. In a com- 

 munication to the Paris Academy of Sciences, 

 Dr. Joubert writes from Brazil that in many 

 of the provinces of that empire the coffee plan- 

 tations are menaced by a minute, thread-like 

 worm, one fourth of a millimetre in length, 

 which attacks the roots, producing thereupon 

 knots and swellings like those on the root of 

 the grape-vine when infested by the phylloxera. 

 The parasite appears to have a preference for 

 the more vigorous plants of seven to ten years' 

 growth, and these quickly succumb to the at- 

 tack, the leaves turning yellow and the whole 

 plant withering. The swellings on the roots 

 contain each a worm, and of the latter as many 

 as fifty millions, it is estimated, will be found 

 preying on a single plant ! 



The Phoneidoscope. If a film of water ren- 

 dered viscid by the mixture of soap be made to 

 close the mouth of a wine-glass, it will, when 

 held in a vertical plane, at first appear uniform- 

 ly white over its entire surface; but, as it 

 grows thinner by the descent of the fluid par- 

 ticles, colors begin to appear at the top. These 

 colors arrange themselves in horizontal bands, 

 and become more brilliant as the thickness of 

 the film diminishes ; finally, the upper part be- 

 comes black, and soon the bubble bursts. But 

 if, instead of remaining at rest, the particles of 

 the film are made to vibrate by sound-waves 

 impinging on the surface, the color phenomena 

 are totally different. These very curious effects 

 can be readily produced without the aid of any 

 artificial instruments. The forefinger and thumb 

 being bent so as to form a circle, a soap-film is 

 drawn across them with the other hand. By 

 turning the wrist, the angle of inclination to 

 the light can be accurately adjusted. A mo- 

 tion of the elbow alters the distance between 

 the film and the mouth of the operator, and, 

 by slightly separating or bringing together the 

 finger and thumb, the tension of the film can 

 be regulated so as to give any desired degree 

 of sensitiveness. If, now, a note be struck by 



the voice, the reflected colors will be seen to be 

 in regular motion, and there will be eddies of 

 color about fixed centers of rotation. The forms 

 presented are of infinite variety and great beau- 

 ty. The contrast between the steady and mov- 

 ing portions of the figures is very striking, and 

 the ettects of changing tint which accompany 

 the progressive thinning of the film gorgeous 

 in the extreme. When the film are about to 

 disappear, patches of inky blackness invade 

 the field, until at last there is sometimes noth- 

 ing left but an ebony background, with here 

 and there a scrap of light. Mr. Sedley Taylor 

 has studied these interesting phenomena with 

 great assiduity, using for the purpose the Tis- 

 ley " phoneidoscope " (from the Greek phone, 

 sound, eidosj figure, and slcopein, to see). The 

 results of his researches are briefly stated in a 

 communication to an English scientific journal. 

 Before giving a resume of them, we will, for 

 the sake of clearness, describe the Tisley pho- 

 neidoscope : An L-shaped cylindrical brass tube 

 is permanently fixed on a wooden stand, with 

 its two limbs vertical and horizontal. The 

 vertical limb terminates in a narrow, flat, cir- 

 cular ring. The open orifice of the horizontal 

 limb is fitted into a caoutchouc tube of equal 

 bore, ending in a trumpet-shaped mouthpiece. 

 For the purpose of supporting the films op- 

 erated on, there is a series of metallic disks 

 pierced with apertures of various shapes and 

 sizes. On covering one of these, by means of 

 a camel's-hair brush, with a weak solution of 

 castile soap, a film of considerable durability 

 is formed. The disk should first be held in a 

 vertical plane, until the colored bands have 

 begun to show themselves, and then laid gen- 

 tly upon the horizontal ring prepared for its 

 reception. Mr. Taylor says : 



The dependence of form on pitch may be shown by 

 alternately striking' with a resined bow two mounted 

 tuning-forks of different pitch, with their resonance- 

 boxes close to the mouthpiece of the phoneidoscope. 

 As long as the same aperture is used and the film kept 

 at one degree of consistency by frequent renewalj each 

 note will call forth its own color-figure. More inter- 

 esting results still are obtained by singing the diaton- 

 ic or chromatic scale, on some single vowel, into the 

 phoneidoscope. 



The effects of quality are observed by employing 

 unison organ-pipes of different timbres ; for example, 

 treble C's belonging to stopped and open diapa- 

 sons, claribella, and hautbois, respectively. By 

 sounding them consecutively in the above order, fig- 

 ures rapidly increasing in complexity are obtained. 



Resultant Figures due to Combined Sounds. If the 

 sounds of two tuning-forks differ by a considerable 

 interval of pitch, they generate, when alternately ap- 



C 1 ' id to the same film, very different figures. When 

 h are applied together, there results a figure dif- 

 ferent from either of those due to each fork by itself 

 a compromise between the two. 



Effects of Beats. When two sounds of very nearly 

 the' same pitch coexist, slow fluctuations of intensity 

 called u beats " are known to be produced. If a film 

 is exposed to the simultaneous action of two sounds 

 so related, the fixed parts of the resulting figure take t 

 up a swaying motion about their mean position, each- 

 complete oscillation synchronizing exactly with one 

 entire beat. 



Dissonance. "When the effect we call discord is 



