June 19, 1890] 



NATURE 



n 



■tion of light, which are, apparently at least, secondary 

 actions due to a reaction of the matter set in motion by 

 the radiation on this radiation. 



Some further diagrams were exhibited, plotted from 

 Hertz's theory by Mr. Trouton, to whom much of the matter 

 in this paper is due. They are here reproduced, and show 

 eight simultaneous positions of the electric and magnetic 

 waves during a semi-oscillation of an electric oscillator. 

 The dotted line shows the electric force at various points, 

 and the continuous line the magnetic force. In the first 

 diagram the magnetic force is at its maximum near the 

 origin, while the electric force there is zero. In the 

 second the magnetic energy near the origin has partly 

 turned into electric energy, and consequently electric 

 force begins. The succeeding figures show how the 

 magnetic force decreases near the origin, while the 

 electric force grows, and the waves already thrown off 

 spread away. The change of magnetic force between 

 Figs. 4 and 5 is so rapid, that a few dashed lines, showing 

 interpolated positions, are introduced to show how it 



proceeds. It will be observed how a hollow comes in the 

 line showing electric force, which gradually increases, 

 and, crossing the line of zero force at about a quarter of a 

 wave-length from the origin, is the source of the electric 

 wave, which, starting with this odds, picks up and remains 

 thenceforward coincident with the magnetic wave. From 

 this origin of electric waves they spread out along with 

 the magnetic waves and in towards the origin, to be 

 reproduced again from this point on the next vibration. 

 These electric and magnetic forces here shown as co- 

 incident are, of course, in space in directions at right 

 angles to one another, as already explained. The corre- 

 sponding diagrams for a magnetic oscillator are got by 

 interchanging the electric and magnetic forces. 



A further experiment was shown to illustrate how 

 waves of transverse vibration can be propagated along a 

 straight hollow vortex in water. It was stated that what 

 seemed a possible theory of ether and matter was that 

 space was full of such infinite vortices in every direction, 

 and that among them closed vortex rings represented 



matter threading its way through the ether. This hypo- 

 thesis explains the differences in Nature as differences of 

 motion. If it be true, ether, matter, gold, air, wood, 

 brains, are but different motions. Where alone we can 

 know^what motion in itself is— that is, in our own brains — 

 we knoiv nothing but thought. Can we resist the con- 

 clusion that all motion is thought.^ Not that contradic- 

 tion in terms, unconscious thought, but living thought ; 

 that all Nature is the language of One in whom we live, 

 and move, and have our being. 



THE CLIMATES OF PAST AGES} 

 II. 



WE need not enter on a detailed description of the 

 other vegetable types of the Coal-measure forma- 

 tion ; we can only note the abundant occurrence of tree- 



' Translation of a Lecture delivered by the late Dr. M. Neumayr before 

 the Society for the Dissemination of Natural Science, at Vienna, on January 

 3, 1889. Continued from p. 151. 



NO. 1077, VOL. 42] 



ferns, and the existence of not very numerous conifers, 

 which amid this strange vegetation are the forms most 

 nearly related to those of our present ^world. 



The geographical extent of this typical flora was 

 extraordinarily great ; we trace it from the shores of the 

 Atlantic through the northern half of the Old World to 

 China, and it is also greatly developed in the eastern half 

 of the United States. There, and in China, are the 

 greatest developments of beds of coal. Besides these, we 

 find similar deposits with nearly the same vegetation in 

 the far north, in the American polar archipelago, in Spitz- 

 bergen, and N^ova Zembla. It is these facts that have led 

 to the conclusion, already mentioned, that in the Carboni- 

 ferous period a uniform climate prevailed from the equator 

 to the pole, together with a dense atmosphere rich in 

 carbon-dioxide, and impenetrable to the solar rays. And 

 yet a simple examination of the facts assures us that all 

 these suppositions are groundless. In so far as regards 

 the character of the flora, we really know nothing of the 

 temperature requisite to the Calamites, Lepidodendra, 



