TRANSACTIONS OF t^ECTlON B. 575 



■fcers of the calcium, the potassium, the chlorine, and the sulphur groups, together 

 with the elements between silver and gold, cadmium and mercury, indium and 

 thallium, and antimony and bismuth, are still waiting to be discovered. We now 

 come to an oasis in the desert of blanks. Platinum, gold, mercury, thallium, lead, 

 and bismuth, all famihar friends, form a close little group by themselves, and then 

 after another desert space the list is closed with thorium (2-3.3) and uranium 

 (240). 



This oasis and the blanlts which precede and follow it may be referred with 

 much probability to the particular way in which our Earth developed into a mem- 

 ber of our solar system. If this be so it may be that on our Earth only these blanks 

 occur, and not generally throughout the universe. 



What comes after uranium ? I should consider that there is little prospect of 

 the existence of an element much lower than this. Look at the vertical line of 

 temperature slowly sinking from the upper to the lower part of the curve ; the 

 figures representing the scale of atomic weights may be also supposed to represent, 

 inversely, the scale of a gigantic pyrometer dipping into the cauldron where suns 

 and worlds are in process of formation. Our thermometer shows us that the heat 

 Las been sinking gradually, and, pari passu, the elements formed have increased 

 in density and atomic weight. This cannot go on for an indehnite extent. 

 Below the uranium point the temperature may be so reduced that some of the 

 ■earlier formed elements which have the strongest affinities are able to enter into 

 combination among themselves, and the result of the next fall in temperature will 

 then be— instead of elements lower in the scale than uranium— the combination of 

 oxygen with hydrogen, and the formation of those known compounds the dissocia- 

 tion of which is not beyond the powers of our terrestrial sources of heat. 



Let us now turn to the upper portion of the scheme. AVith hydrogen of 

 atomic weight = 1 , there is little room for other elements, save perhaps for hypothetical 

 helium. But what if we get ' through the looking-glass,' and cross the zero-line in 

 search of new principles— what shall we find the other side of zero ? Dr. Car- 

 nelley asks for an element of negative atomic weight ; here is ample room and vero-e 

 «nough for a shadow series of such uusubstantiahties. Helmholtz says that elec- 

 tricity IS probably as atomic as matter ; ' is electricity one of the negative elements ? 

 and the lummiferous ether another ? Matter, as we now know it, does not here 

 exist ; the forms of energy which are apparent in the motions of matter are as yet 

 only latent possibilities. A substance of negative weight is not inconceivable.* 

 But can we form a clear conception of a body'which combines with other bodies in 

 proportions expressible by negative quantities ? 



A genesis of the elements such as is here sketched out would not be confined to 

 our little solar system, but would probably follow the same general sequence of 

 events in every centre of energy now visible as a star. 



Before the birth of atoms to gravitate towards one another, no pressure could be 

 exercised ; but at the outskirts of the fii-e-mist sphere, within which all is protyle— 

 at the shell on which the tremendous forces involved in the birth of a chemical 

 element exert full sway— the fierce heat would be accompanied bv gravitation 

 sufiicient to keep the newly-born elements from flving oft' into space. ' As tempera- 

 ture increases expansion and molecular motion" increase, molecules tend to fly 

 asunder, and their chemical affinities become deadened ; but the enormous pressure 

 of the gravitation of the mass of atomic matter outside what I may for brevity call 

 the birth-shell_ would counteract this action of heat. 



Beyond this birth-shell would be a space in which no chemical action could take 

 place, owing to the temperature there being above what is called the dissocia- 

 tion-point for compounds. In this space the lion and the lamb would lie down 



> ' If we accept the hypothesis that the elementary substances are composed of 

 atoms, we cannot avoid concluding that electricity also, positive as well as negative 

 is divided into definite elementary portions, which behave like atoms of electri- 

 city.' — Helmholtz, Faraday Lecture, 1881. 



^'I can easily conceive that there are plenty of bodies about us not subject 

 to this intermutual action, and therefore not subject to the law of gravitation '—Sir 

 Oeorge Au-y. Faraday's Life and Letters, vol. ii. p. 354. 



