Experimental investigation of the spirit manifestations, [electronic ...

Of MATTKR, MINI), AND SPIRIT. 377radiation involves ;lines of particles proceed from the hotter points to thecolder ones.1834. The arrangement of the particles of caloric, which was originally,in my view, confined to the sublunary creation, appears of necessity tobelong to the luminiferous ether, required by the theory ascribing light toundulations, though the last-mentioned medium must be endowed withubiquity as above stated, so as to abound in every part of space throughwhich light reaches the eye.1835. The undulatory hypothesis supposes that a wave-like motion beingimparted to a row of particles, by a luminous point in the surface of theluminous body, is transmitted, like the sound producing waves in the air,to the other end of the row.1836. This undulatory progression has been roughly illustrated by thetransitory serpentine movements which may be made ina cord, stretchedlike a clothes-line between the tops of posts.1837. In order to make this illustration elucidate the conception which Iadvance, we have only to suppose that the cord, instead of being attachedto the post, should be drawn rapidly over pulleys, and, while thus actuated,be subjected to a cause of undulatory vibration. It may be conceivedthat, by this process, the ethereal particles, while performing all which theundulatory theory requires, might at the same time perform all requiredby that of emission and material calorific radiation. Directed upon a vaporizableliquid, the undulations might perform the part of sensibleheat; the ethereal particles, successively combining, might furnish thelatent heat requisite to the constitution of vapour.1838. Agreeably to Newton, the seven colours of the spectrum are dueto as many different kinds of radiant particles of various refrangibility, orsusceptibility of being bent from the rectilinear path when passed throughthe same refracting medium.*1839. -According to the undulatory theory, the colours are caused bydiversities in the undulations producing them. Retaining this feature, thelast-mentioned hypothesis, as modified by myself, appears to be competentto explain the phenomena of light as well as those of vaporization, producedby calorific radiation, since not only is any vaporizing liquid subjectedto the transient effect of the undulations, but also may combine withthe ethereal particles as they come into contact with it.1840. Thus modified, the rationale of the rainbow, or prismatic spectrum,would not be that the colours indicate as many varieties of originalradiant particles, but that they are to be explained agreeably to the undulatoryhypothesis, which ascribes them to as many varieties in the undulations,just as the notes in music are ascribed to diversities of vibration.* Latterly, Sir David Brewster has conceived that only three elementary species oflight are requisite, according to the theory of emission, to perform all the ofBces whichNewton ascribed to seven.