August i8, 11898] 



NATURE 



167 



LETTERS TO THE EDITOR 



[The Editor does not hold himself responsible for opinions eX' 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of rejected 

 ntanuscripis intended for this or any other part of NATURE. 

 No notice is taken of anonymous communications.^ 



Potential Matter.— A Holiday Dream. 



When the year's work is over and all sense of responsibility 

 'has left us, who has not occasionally set his fancy free to dream 

 about the unknown, perhaps the unknowable ? And What 

 should more frequently cross our dreams than what is so per- 

 sistently before us in our serious moments of consciousness — the 

 universal law of gravitation. We can leave our spectroscopes 

 and magnets at home, but we cannot fly from the mysterious 

 force which causes the rain-drops to fall from the clouds, and 

 our children to tumble down the staircase. . What is gravity? 

 We teach our students to accept the fact and not to trouble 

 about its cause — most excellent advice — but this is vacation 

 time, and we are not restricted to lecture-room science. 



Lasage's particles are not satisfactory ; they are too material- 

 istic for the holiday mind ; but I have always been fascinated 

 by a passage occurring somewhere in Maxwell's writings, where 

 Lord Kelvin is quoted as having pointed out that two sources 

 or two sinks of incompressible liquid will attract each other with 

 the orthodox distance law. 



Let us dream, then, of a world in which atoms are sources 

 through which an invisible fluid is pouring into three-dimensioned 

 space. What becomes of this fluid ? Does it go on for ever 

 increasing the volume of that all-pervading medium which 



• already fills a vast, but not necessarily infinite, space ? When 

 we speak of the constancy of matter, we mean only the con- 

 stancy of inertia, and how are we to prove that what we call 



'matter is not an endless stream, constantly renewing itself and 

 pushing forward the boundaries of our universe ? The concep- 

 tion of atoms as sources of fluid does not, however, necessarily 



'involve such a perpetual increase of substance, for an equal 

 number of sinks may keep withdrawing the increment. 



These sinks would form another set of atoms, possibly equal 

 to our own in all respects but one ; they would mutually gravi- 

 tate towards each other, but be repelled from the matter which 



■we deal with on this earth. If matter is essentially dynamical, 

 and we imagine the motion within an atom to be reversed, the 

 question arises whether the reversed motion is similar to the 



• original one ; in other words, whether the new atom so formed 

 may by a change of position be brought into coincidence with 

 the old one. And if this is not the case, we must ask ourselves 

 whether the new atom will behave gravitationally like the old 

 one. If atoms are sources of liquid there would be no recipro- 

 city, and the sinks would form another and so far unrecognised 

 world. But sources and sinks compel us to the supposition of 

 a fourth dimension, which belongs to the domain of nightmares, 

 not of dreams, and we try to shake ourselves free from the 



I idea. 



I, for one, cannot quite succeed in this effort, for something 

 has been left behind, which is not easily got rid of, when once 

 its symmetrical beauty is perceived. Surely something is 

 wanting in our conception of the universe. We know positive 

 and negative electricity, north and south magnetism, and why 

 not some extra terrestrial matter related to terrestrial matter as 

 the source is tn the sink, gravitating towards its own kind, but 

 driven away from the substances of wliich the solar system is 

 composed. Worlds may have formed of this stuff", with elements 

 and compounds possessing identical properties with our own, 

 ■undistinguishable in fact from them until they are brought into 

 each other's vicinity. If there is negative electricity, why not 

 negative gold, as yellow and valuable as our own, with the 

 same boiling point and identical spectral lines ; different only in 

 so far that if brought down to us it would rise up into space with 

 an acceleration of 981. The fact that we are not acquainted 

 with such matter does not prove its non-e.dstence ; for if it ever 

 existed on our earth, it would long have been repelled by it and 

 expelled from it. Some day we may detect a mutual repulsion 

 between different star groups, and obtain a sound footing for 

 what at present is only a random flight of the imagination. 



Even now some might argue that we possess some substantial 

 evidence of repulsive forces. In our glorification of the New- 

 tonian system we are apt to overlook some obvious facts which the 

 .law of gravitation fails to explain. One of these is the rota- 



NO. 1503, VOL. 58] 



tional velocity of our solar and of many stellar systems, which 

 cannot be self-generated. Unless we threw our laws of 

 dynamics overboard, or imagine the rotation to have been im- 

 pressed by creation, we must conclude that some outside body 

 or system of bodies is endowed with an equal and opposite 

 angular momentum. What has become of that outside body, 

 and how could it have parted company with our solar system, 

 if attractive forces only were acting? Another unexplained 

 fact is found in the large velocities of some of the fixed stars, 

 which, according to Prof. Newcomb's calculations, cannot be 

 explained by giavitational attractions only. 



The atom and the anti-atom may enter into chemical com- 

 bination, because at small distances molecular forces would 

 overpower gravitational repulsions. Large tracts of space 

 might thus be filled unknown to us with a substance in which 

 gravity is practically non-existent, until by some accidental cause, 

 such as a meteorite flying through it, unstable equilibrium is 

 established, the matter collecting on one side, the anti-matter 

 on the other until two worlds are formed separating from each 

 other, never to unite again. 



Matter and anti-matter may further coexist in bodies of small 

 mass. Such compound mixtures flying hither and thither 

 through space, coming during their journey into the sphere of 

 influence of our sun, would exhibit a curious phenomenon. 

 The matter circulating in a comet's orbit, the anti-matter re- 

 pelled and thrown back into space, forming an appendage which 

 is '.ways directed away from the sun. Has any one yet given 

 a satisfying explanation of comets' tails ; is the cause of coronal 

 streamers known, and can any one look at a picture of the great 

 prominence of the 1885 eclipse, and still believe that gravita- 

 tional attraction or electric repulsion is sufficient to account for 

 its extravagant shape ? But this is not a scientific discussion. 

 I do not wish to argue in favour of the existence of anti-atoms, 

 but only to give my thoughts a free course in the contemplation 

 of its possibility. 



What is inertia ? When the atom and anti-atom unite, is it 

 gravity only that is neutralised, or inertia also ? May there not 

 be, in fact, potential matter as well as potential energy ? And 

 if that is the case, can we imagine a vast expanse, without 

 motion or mass, filled with this primordial mixture, which we 

 cannot call a substance because it possesses none of the attributes 

 which characterise matter ready to be called into life by the 

 creative spark ? Was this the beginning of the world ? Is our 

 much-exalted axiom of the constancy of mass an illusion based 

 on the limited experience of our immediate surroundings? 

 Whether such thoughts are ridiculed as the inspirations of mad- 

 ness, or allowed to be the serious possibilities of a future science, 

 they add renewed interest to the careful examination of the 

 incipient worlds which our telescopes have revealed to us. 

 Astronomy, the oldest and yet most juvenile of sciences, may still 

 have some surprises in store. May anti-matter be commended 

 to its care ! But I must stop — the holidays are nearing their 

 end — the British Association is looming in the distance ; we 

 must return to sober science, and dreams must go to sleep till 

 next year. 



Do dreams ever come true ? Arthur Schuster. 



Live Frog taken out of a Snake. 



Your correspondent. Colonel Major, may be interested to 

 hear of another instance of a Batrachian returning alive from 

 the stomach of a snake. A grass snake of about 24 inches, 

 kept in captivity, had not fed for three weeks : it was then given 

 a very large specimen of the common frog, full grown ; this was 

 swallowed at once, in the usual way by taking the hind leg first. 

 In about an hour and a half the frog was a third of the way 

 down the snake's body. Then, on the snake being played with 

 and handled, after some minutes the lump began to move up 

 rapidly towards the head of the snake, the mouth opened and 

 out slid the frog; rather oft' colour, and not very happy- looking, 

 but quite able to hop about in a shuffling fashion, though de- 

 cidedly shaky on his legs. To an amphibian imprisonment 

 without air could not be very hurtful for a few hours, were it not 

 for the poison of the gastric juices. When the grass snake was 

 left agam with the frog it re-swallowed its prey. A snake will 

 often take half an hour swallowing a frog : the distension of 

 the jaws during the operation is extraordinary to witness. In 

 about an hour's time the frog will be a third of the way down 

 the snake's body. Rose Haig Thomas. 



Badenweiler, August 14. 



