108 SCIENCE. [1899.
atoms, forming ions, and liberating uncharged atoms of the metal. Fatigue of fluorescence would be due to the electrons, already lodged* repelling those that followed. Rontgen rays would be due to internal vibrations of the electrons, occasioning waves of very small length,, irrefractible because capable of passing freely through molecular inter- spaces, liable to absorption at molecular surfaces, and subject to diffusa scattering instead of reflection.
The originator of this theory remarks that it involves the possibility of an anodic stream of positive electrons. Lord Kelvin, too, finds that in addition to the specularly reflected rays the antikathode reflector gives off, under certain conditions, well-defined rays, normal to ita surface, that cause fluorescence of the glass. M. Villard has reason to believe that hydrogen plays a prominent part in the production of kathodic rays.
In the Hertz phenomenon the oscillator produces waves of three kinds ; a wave of transverse electric force, an electric wave parallel to the axis of the force, and a wave of magnetic force. The great ampli- tude of the waves that Signor Marconi has utilised in wireless telegraphy causes them to wrap round an obstacle. A substance that is really opaque to them seems to be transparent because it casts no " shadow." Though a closed cage of metal or of metallic gauze excludes them, they get through any chink or slit. Experiments made in syntony, with a view to attune particular transmitters to particular receivers, have been hitherto unsuccessful.
jEtherology would be a juster name than physics for these investiga- tions that have become so largely transcendental. It has even been suggested that the theory of a two-fluid ether is required to explain many pressing difficulties. And when complex dynamical systems have to be dealt with in a compound ether, the problem of molecularity wilt be a joy for ever.
Physiology.
The average electrical resistance of healthy human blood at 60° Fahr. is 550 ohms. In pernicious anaemia it is reduced to half this value, for the reason, as supposed, that the blood in that disease contains an excess of salts due to destructive metabolism.
A strip of vena cava from the terrapin's heart may be kept in rhythmic action for upwards of two days in a bath which contains sodium chloride, potassium chloride, and calcium chloride in propor- tions normal to the blood. From this fact Mr. Howell argues that the heart's energy is derived from a store of material within its own tissue, and that it will continue to beat until this is consumed if supplied with an adequate stimulation. The normal stimulus is obtained from calcium compounds ; potassium salts are required for rhythm ; whilst the sodium chloride is necessary to make the solution isotonic with the blood, in order that osmotic relations may be duly maintained. This bath, however, will not keep up the action of the terrapin's ventrical, which is insusceptible to saline stimulation; and the important con- clusion follows that the heart's normal rhythm is started at the venous end.
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