282 



KNOWLEDGE. 



[December 1, 1896. 



a brief mention in this concluding article. To fix our 

 ideas we will suppose that we are dealing with the familiar 

 artery which gives the pulse of the wrist. At each boat 

 of the heart, blood is pumped into the near end of the 

 artery and the valve is quickly shut. Very quickly after- 

 wards an extra quantity of blood is forced from the artery 

 into the veins and capillaries. This is not the particular 

 dose of tluid which has just entered the artery, but a 

 discharge from the other end of the stream, where a pulse 

 is felt almost immediately after the throb of the heart. 

 The push, or impulse, is transmitted from point to 

 point along the artery, not as hydrostatic pressure is 

 transmitted by an incompressible fluid, but after the 

 manner of a wave. For the blood is not enclosed 

 in a rigid pipe, but in a flexible tube, so that, 

 although the tluid does not yield to pressure, the tube 

 does, and the end nearest the heart expands to accommo- 

 date the extra dose of fluid. Expansion of the tube is, 

 however, followed by contraction, for the tube is elastic 

 though yielding. The next portion of the tube then 

 expands, and so on, a billow travelling down the artery. 

 When the billow reaches the wrist it can be both seen and 



FiQ. 3. — Pulse Tnuing of Diseased Heart. 



felt. It has passed the wrist before the next dose of fluid 

 IS delivered from the heart, so that only one billow is ever 

 traversing the artery. The profile of the billow is recorded 

 in an exaggerated manner upon the well-known pulse 

 tracings. These provide a permanent record of the con- 

 dition of a patient's pulse which is convenient for reference. 

 Each of the pulse tracings shown in Figs. 3 and 4 records a 

 number of beats ; the wave is travelling to the right ; from 

 trough to trough is a complete pulsation. 



***** 

 The brain is kept in touch with the external world by 

 some kind of wave motion, the mechanism by which the 

 sensory nerves transmit their message. The velocity of 

 the wave, which is always considerable, varies to some 

 extent in different people, as one would naturally expect. 

 Responding to the wave of feeling, transmitted by the 

 sensory nerves, is the wave of will, whereby the motor 

 nerves transmit to the muscles the message of the brain. 



Fia. 4. — Pulse Tracing of Fairly Normal Heart. 



Whether mind can act upon mind, otherwise than by 

 means of the ordinary senses, is a much debated question. 

 Some aspects of this question of telepathy come within the 

 proper scope of physical science. It comes within the 

 province of physical science, for instance, to inquire 

 into the possible extra-sensual means of action of one 

 brain upon another. Space is filled with a medium, 

 known to science, which has a wonderful power of 

 transmitting very various disturbances without loss and 

 with great swiftness, and one would naturally inquire first 

 whether the known modes of motion of ether are such as 

 might account for telepathic phenomena, on the supposition 



that the active brain is capable of disturbing the ether. 

 Now one of the most remarkable points about the narratives 

 of, say, phantasms of the dying, is that the intensity of 

 the recorded impressions scarcely diminishes with distance, 

 even though the distances vary from one mile to eight 

 thousand miles. Waves rndiiiiinij from the brain will 

 therefore not explain the recorded phenomena, for even if 

 the motion be transmitted without loss, the expansion of 

 the wave front would rapidly diminish the intensity. 

 Nothing else than a motion or disturbance confined to a 

 channel will do, as happens, for instance, in the dis- 

 turbance and reproduction of disturbance between the 

 sending and receiving parts of a telephone. These are 

 connected by the telephonic wire. I am not aware 

 that anything has been found corresponding to a tele- 

 pathetic wire. 



Principal References for " Waves," as treated in Knowledge, for 

 1896, by Vauqhak CoENian. 



1. Aberckomby, Hon, Enlph, Prof. Phys. Soc. (London), Vol. IX. (1887-8), 

 p. 1.50, " Ocean Waves." 



2. Airy, Sir G. B., " Encycl. Metropolitana " (184.5), "Tides and Waves." 



3. Boys. Prof. C. V., Salurc, Vol. LII., p. 272, "Wave Leuitth and Velocity." 

 For " Wave Tracls ol Bullets," see pamphlet from Newton & Co., Strand, 

 London. 



4. Darwi.v. Prof. G. H., "Eucycl. Brit.," Ninth Edition, " Tides." Pnc. Roy. 

 .Soc, XXXVI.. 1883-4, "Ripple Marli." 



5. Dixon, Prof. H. B., Phil. Ti-ans., 180:!, "Explosion Wave." 



fi. Foster, Prof. Michael, " Physiology," " Pulse and Nerve Waves." 



7. Froude, Mr. E., Proc. Inst. Nmal Architects, April, 1881, " Wave-maliing 

 Resistance of Ships." 



8. Froude, Mr. Wm., Proc. Inst. Kaval Architects, 1861, "Rollins of Ships." 



9. Glazerrook, Mr., "Test-Book of Physical Optics," "Wave Fronts in 

 Crystals." 



10. Helmholtz, Prof, von, Salure, 1889. Vol. XLI., and F. Waldo's "Modern 

 Meteorology " (189.3). pp. '236 and 355 cl scij., " Interaction of Air and Water, 

 and Formation of Billows of Ail'." Also "Lectures," Vol.1., " Form of 

 Sound Waves in Air." 



11. Hertz, Prof. H., Papers translated by D. E, Jones, D,Sc,," ElectricWaves." 



12. Kelvin, Lord, PI' it. Mag., November, 1871, "Ripples;" and Nature, Vo], V., 

 Novemlaer 2nd, 1871. Phit. Maij., October, November, December, 1.886, 

 and January, 1887, "Stationary Waves in Flowing Water." "Popular 

 Lectures and Addresses," Vol, ill,, " Tides " and " Ship Waves." 



13. MacGowan. Mr,, Phil. Mag., July, 1891, " Solitary Wave." 



14. Maxwell, Prof. J. C, " Encycl. Brit.," Ninth Eilition, "Capillarity"; 

 also " Text- Book on Heat" (Lon^-mans). 



15. MiCHELL, Sir J. H., Phil. Mat:., November, 1893, "Highest Waves in Water." 



16. Rayleigh, Lord, Nature, Vol. XIV., 1876, pp. 32-33, "Perception of the 

 Direction of a Source of Soimd." Proc. Kay. Soc, Vol. XXVI., 18'7, 

 pp. 34S-249, " Amplitude of Sound Waves." Proc. Roy. Soc, Vol. XXIX., 

 1879, pp. 71-97, "Capillary Phenomena of Jets." 



17. Reynolds, Prof. Osborne. Nature, Vol. XVI., 1877, p. 343, " Rate of Pro- 

 gression of Groups of Waves." 



18. lioYAL Society's Report upon the Eruption of Krakatoa. " (Elastic) Air 

 Waves and Seismic Sea Waves." 



19. Russell, Mr. J. Scott, B. A. Bepr,,-!, Vol. XIV. (1844 Meeting), " Report on 

 Waves" (contains account of solitary, capillary, and standing waves). 



20. Schmidt, Dr. A., Nature, October 24th, 1895, pp. 631-C33, Dr. Schmidt's 

 "Theory of Eiirtliquake Waves." 



21. ScORESBY, Dr., B. A, Report (1850 Meeting). Part II., pp. 26-31, "Atlantic 

 Waves," 



22. Tait, Prof. " Encycl. Brit.," Ninth Edition, "Waves," and " Mechanics." 



THE BEECH. 



By George Paxton. 



THE beech {Fra.vinus excelsior) is a magnificent 

 tree, which vies with the oak, in some respects, 

 for the proud title, " King of the Forest." 

 Although not " every inch a king," he may be 

 styled a noble forest prince. 

 The beech is only a doubtful native of England, and 

 is not indigenous to Scotland or Ireland, although now so 

 common in these islands. It is found in forests in Central 

 and Southern Europe, Asia, North and South America, 

 and even in Australia. In Switzerland it occupies the 

 south sides of the mountains, and it is the national tree of 

 Denmark. In Britain it grows to a large size, occasionally 

 attaining a height of one hundred and twenty feet, but 

 is oftener seen from sixty to eighty feet, with a girth of 

 twelve to sixteen feet. Fig. 1 represents a beech growing 

 on the banks of the Kiver Ayr. This tree has a girth of 

 over eighteen feet at five feet from the ground, with a 

 height of about ninety feet. 



