June 1, 1894.] 



KNOWLEDGE. 



125 



the experiments point to the conclusion that the earth 

 carries the ether with it. 



Prof. 0. J. Lodge has recently been making experiments 

 to find if he can detect any motion of the ether caused by 

 that of neighbouring matter. He uses two steel discs 

 about a yard in diameter, clamped together with a space 

 of one inch between ; these are made to spin round very 

 fast. Then a parallel beam of light is split into two by a 

 semi-transparent mirror, i.e., a piece of glass silvered so 

 thinly that it lets half the light pass through, and reflects 

 the other half, and the two portions of this di\'ided beam 

 are sent by successive reflections round and round the 

 space between the discs, in opposite directions. After 

 traversing thus a distance of from twenty to forty feet, 

 they are finally made to meet and enter a telescope. 

 In general, the lengths of the paths of the two portions 

 of the beam differ very slightly, and thus they interfere. 

 It is observed whether the motion of the discs is able to 

 cause displacement of the interference bands, but Prof. 

 Lodge could detect no true shift of the bauds. He says : 

 " Of real reversible shift, due to motion of the ether, I see 

 nothing. I do not believe the ether moves. It does not 

 move at a five-hundredth part of the speed of the steel 

 discs." Circular saws, railway trains, &c., he thus con- 

 cludes, do not carry the ether with them ; their motion 

 does not seem to disturb it at all. The presumption is 

 that the same is true of the motion of the earth. Prof. 

 Lodge thinks that " if moving matter disturbs ether in its 

 neighbourhood at all, it does so by some minute action 

 comparable in amount, perhaps, to gravitation, and possibly 

 by means of the same property as that to which gravitation 

 is due — not by anything that can fairly be likened to 

 ethereal viscosity." 



Prof. Lodge has recently been able to increase the 

 velocity of his discs to three thousand revolutions per 

 minute, but even with this rapid rotation nothing which 

 can be attributed to a drag of the ether has been detected. 



On the other hand, Mr. Michelson concludes from his 

 experiments that the relative velocity of the earth and the 

 ether is probably less than a sixth of the earth's orbital 

 velocity, and certainly less than one-fourth. Thus the 

 question of the connection of the ether with gross matter, 

 and the relation of its motion to that of the earth and the 

 heavenly bodies, is still by no means settled. 



Not only has the luminiferous ether been applied to 

 account for the propagation of waves of light, and 

 for the phenomena of electrification by supposing this 

 to be due to stresses set up in it, but Lord Kelvin 

 has suggested that the ultimate atoms of matter may 

 consist of vortices or whirlpools in the ether. He 

 has pointed out that by means of motion alone, in a 

 fluid destitute of elasticity, a virtual elasticity may be 

 produced. It is well known that a quasi-rigidity may be 

 conferred on a limp chain by causing it to rotate rapidly. 

 If when rapidly revolving the chain be struck, a permanent 

 kink or bend is made in it which retains its form while 

 the rotatory motion lasts. Moreover, two smoke rings 

 when they collide rebound from each other as if they 

 were elastic, this appearance of elasticity being conferred 

 on them by their motion. Thus Lord Kelvin's hypothesis 

 in his kinetic theory of matter is that atoms are not hard 

 and solid, but that they consist of rotatory rmgs or 

 whirls in an incompressible frictionless fluid which is 

 perfect and homogeneous, this fluid being the ether, and 

 difi'erences in the elementary atoms are due to difl'erences 

 in the character and behaviour of these vortices, which 

 may be linked together in various ways. A serious 

 objection to the kinetic theory of gases, by which they are 

 represented as cf^isisting of hard solid spheres flying about 



and colliding with each other, has been pointed out by 

 Lord Kelvin. It is that the effect of the collisions must 

 be to gradually convert the energy of translation into 

 shriller and shriller vibrations of the molecule, and that 

 finally all the translational energy will be changed into 

 this form. Thus on the elastic solid hypothesis of the 

 atom the result is not much different from what it would 

 be if there was imperfect elasticity. If there is no 

 tendency of this sort in the case of the vortex atoms, a 

 serious difficulty would be got over. Such atoms, more- 

 over, would possess the properties of unchangeability and 

 indivisibility ; they cannot be cut, for they would simply 

 wriggle away from the cutting instrument. They are 

 capable of vibrations, and mutual action at a distance 

 can be explained by continuous action through the inter- 

 vening ether. 



THE GENESIS OF FLOWERS. 



By the Rev. Alex. S. Wilson, M.A., B.Sc. 



THE flowers most generally known are brightly 

 coloured blossoms adapted for insect fertilization ; 

 only these require to attract insects, which is the 

 end served by the perfume and conspicuous 

 colouring. Very many plants, however, bear 

 blossoms so small and obscurely coloured that they are 

 commonly either entirely overlooked or not reckoned as 

 flowers at all. The wind-fertilized flowers of the dock and 

 nettle have no occasion for the services of insects, and are 

 destitute of honey, odour, and brilliant petals. Still more 

 insignificant in appearance are the little self-fertilizing 

 cleistogamic flowers which, towards the end of the season, 

 are produced on the dog-violet. All three kinds possess 

 stamens and pistils, and are therefore recognized as flowers 

 by botanists. Besides stamens and pistils, which are the 

 essential organs of a flower, petals and sepals are usually 

 present. The petals collectively compose the corolla, the 

 sepals the calyx ; both together being spoken of as the 

 floral envelopes or perianth. Occasionally, as in the ash, 

 the flower is reduced to its essential organs, the floral 

 envelopes being absent. Plants bearing flowers, whether 

 with or without floral envelopes, are designated phanero- 

 gams or flowering plants ; they constitute the highest 

 division of the vegetable kingdom. Ferns and mosses, 

 again, are examples of the cryptogamic or flowerless 

 class ; they never bear flowers or seeds, but are propagated 

 by minute reproductive bodies termed spores. This class 

 is divided into thallophytes and vascular cryptogams. 

 The organization of a thaUophyte is very simple ; the 

 plant-body of a fungus or sea-weed, for example, consists 

 entirely of similar cells, and externally shows no distinc- 

 tion into root, stem, and leaf. The structure of a vascular 

 cryptogam, such as a club moss, horsetail, or fern, is more 

 complicated ; both cells and vessels enter mto the com- 

 position of its tissues, and externally the distinction of 

 stem and leaf is apparent. Phanerogams also admit of a 

 twofold division into gymnosperms and angiosperms ; 

 conifers, cycads and yews are gymnospermous, having 

 naked seeds, exposed either on the ends of branches or on 

 the surface of open scales. All ordinary flowering plants 

 l^roduce their seeds in the interior of a closed ovary, as the 

 lower part of the pistil is called ; from this peculiarity 

 they are termed angiosperms. 



Only the remains of thallophytes have hitherto been 

 discovered in the oldest Paloeozoic rocks. Vascular 

 cryptogams appear in the Silurian strata, attain their 

 maximum in the Carboniferous age, and in succeeding 

 formations are gradually displaced by gymnosperms. The 



