SCIENCE. 



623 



to the north pole, ihe phase of compressing to the south 

 pole. Now bring to one of these pulsators which can 

 turn freely around a vertical axis which acts as its sup- 

 port, while allowing the vibration to continue, a second 

 pulsator held in the hand. 



If we put in juxtaposition, in the liquid, the two pulsa- 

 tors whose phases are of the same kind, synchronous, 

 poles of the same name will always be in juxtaposition, 

 there will be attraction, the movable pulsator turning on 

 its axis, will tend to approach the pulsator held in the 

 hand by the experimenter, and it will follow it if it is 

 moved. If the phases are changed, so that they are in- 

 verse, opposite poles will be together, and there will be 

 repulsion. In the one case as in the other, the attractive 

 or repulsive force is proportional to the intensity of the 

 pulsations and inversely proportional to the square of the 

 distances. In both cases, the hydro-dynamic effect is the 

 reverse of the magnetic effect : similar phases attract 

 (poles of the same name repel each other), different 

 phases repel (opposite poles attract). 



The same experiment is repeated with the oscillators 

 (Fig, 2, No. 3) ; by presenting to a vibrating sphere, mov- 

 able on an axis, a second vibrating sphere, attraction or 

 repulsion is produced according to the synchronism or 

 the discordance of vibration, which the parts of the sphere 

 in juxtaposition present at each instant. 



Fig. 2. Apparatus for reproducing pulsations and oscillations in a 

 liquid. 



i. Simple drum. 2. Double drum. 3. Sphe es. 



For these phenomena, the arrangements for which can 

 be varied, M. Bjerknes has a collection of apparatus 

 almost complete, representing inverse analogies to the 

 phenomena of the reciprocal action of two permanent mag- 

 nets. A result similar to the action of a magnet on a 

 piece of soft iron can be obtained. By presenting, in 

 the water, a small metallic sphere to a pulsator, or to an 

 oscillator, the small sphere will be attracted. 



The effects of diamagnetism are shown by means of 

 a small sphere lighter than the water, maintained at the 

 middle of the liquid by a thread attached to a weight 

 which ballasts it. By bringing a pulsator or an oscillator 

 near this sphere, the latter will be repulsed. 



From these experiments, and from others the details of 

 which cannot be given, M. Bjerknes concludes that the 

 motion in water of a vibrator (pulsator or oscillator) pro- 

 duces in this fluid a real magnetic field with its lines of 

 force, presenting, but always inversely, phenomena sim- 

 ilar to those of diamagnetism, paramagnetism, magnetic 

 interference, etc. 



M. Bjerknes has even succeeded in tracing the direc- 

 tions of the lines of force produced in the liquid, by means 

 of the arrangement shown in fig. 3. For this a light bowl 

 sustained by an elastic rod is placed in the middle of the 



liquid ; this bowl having no motion of its own will take 

 exactly the direction of the oscillation of the ambient 

 medium. If it is surmounted by a small brush, the latter 

 will paint faithfully and automatically on a sheet of glass 

 the lines of force of the field under the influence of which 

 it oscillates. 



M. Bjerknes commenced by submitting all these ques- 

 tions to analysis, and the results of his experiments are 

 only the rigorous confirmation of his calculations. In 

 that which concerns the analogy between the electric 

 currents and hydrodynamic action, M. Bjerknes recog- 

 nized that the question is not as advanced as in magnetic 

 phenomena. 



In order to produce more complex movements, the 

 vibrators are no longer suitable. M. Bjerknes attempted 

 to realize them in a viscous liquid, and striking analogies 

 were found between the lines produced by hydro-dynamic 

 phenomena under these conditions and the lines obtained 

 by real currents under corresponding conditions, but the 

 results obtained are not accurate enough to enable one to 

 form an opinion. 



What now can be concluded from the experiments of 

 M. Bjerknes? The fact indisputably established is as 

 follows : 



Mechanical vibrations produced in a liquid medium 

 cause phenomena analogous, but inverse, to the magnetic 



Fig. 3. Apparatus of M. Bjerknes for tracing automatically the lines of 

 hydro-dynamic force. 



phenomena produced by magnets. From this can be 

 concluded, by analogy, but not absolutely, that mole- 

 cular vibrations of a different nature can produce direct 

 phenomena. 



If this is not a new proof, in the exact meaning of the 

 word, of the vibratory nature of magnetic and electric 

 effects, it is at least a powerful argument applied to this 

 view, accepted at the present time by most physicists. — 

 Translated from La Nature. 



M. Plateau describes as " un petit amusement" the fol- 

 lowing experiment : — a flower like a lily, with six petals 

 each about an inch long, was constructed in outline in thin 

 iron wire, the wire being first slightly peroxidised by dip- 

 ping for an instant into nitric acid. This wire frame was 

 then dipped into a glyceric-soap-solution, which, when it 

 was withdrawn, left soap-films over the petals. The stalk 

 was then set upright in a support, and it was covered by a 

 bell-glass to protect it from air-currents. In a lew moments 

 the most beautiful colo r s made their appearance. If the 

 solution is in good condition the films will last for hours, 

 giving a perpetual play of color over the flower. 



