484 EEPORT— 1882. 



promise he holds out, will enable iis to solve many questions wliich are difficult to 

 answer with our present appliances. 



But to return to the chemical elements : the spectroscope has in the last few 

 years revealed to us several new metals. I will not venture to say how many, for 

 when several new metals more or less closelj' allied are discovered at the same time, 

 the process of sifting out their differences is necessarily a slow one. We cannot 

 tell yet whether any of them are to fill gaps in Mendelejefl"'s table, .and so add 

 strength to the conviction that there is a natural relation between the atomic 

 weights and the chemical characters of our elementary substances, or whether they 

 will add to the embarrassment in which we already find ourselves with regard to 

 the relations of the cerium group of metals ; whether we may welcome them as the 

 supporters of order, or deprecate their coming as authors of confusion. Granting 

 that the cliemical characters of an element are connected with its atomic weight, 

 we ha^e, however, no right to assume them to be dependent on that factor alone. 

 Why may there not be elements which, while they differ as little in atomic weight 

 as do nickel and cobalt, are, on the other hand, so similar to one another in all 

 characters that their chemical separation is a matter of the greatest difficulty, and 

 their difference only distinguishable by the spectroscope ? The spectra may be 

 thought to suggest so much, and how shall we decide the question ? At any 

 rate the complications of the spectroscopic problem can only be unravelled by 

 the united efforts of the chemists and physicists, and by the exercise of extreme 

 caution. 



I cannot dismiss the subject of chemical dynamics without alluding to the in- 

 genious theory by which the President of the Association has proposed to accoimt 

 for the conservation of solar energy. He supposes planetary space to be pervaded 

 by an atmosphere which, except where it is condensed by the attraction of the sun 

 and planets, is in a highly attenuated state. The sun and planets communicate 

 some of their own motion of rotation to the atmosphere condensed about them, and 

 he supposes that in this way an action like that of a blowing fan is set up, by which 

 the equatorial part of the sun's atmosphere acquires such a velocity as to stream 

 out to distances beyond the earth's orbit, while an equal quantity of gas is drawn in 

 at the poles to maintain equilil)rium. The gases thus driven to a distance in planet- 

 ary space will of course be enormously expanded and higlily attenuated, and in 

 this state Dr. Siemens thinks that such of them as are compound may be decomposed 

 by absorbing the solar radiation, and thus the kinetic energy of tlie sun's rays be 

 converted into the potential energy of chemical separation. The separated elements, 

 or partial compounds, will in the circulation produced by the fanlike action of the 

 solar rotation be carried back to the polar regions of the sun as fuel to maintain 

 his temperature by condensation and re-combination. I will not discuss the me- 

 chanical part of this theory further than to remarlc that the faulike action can 

 only be carried on at the expense of the energy of the sun's rotation, which 

 must in consequence be continually diminishing, and must in time become too 

 slow to produce any sensible projection of the atmosphere into distant regions 

 of planetary space. As to the chemical side of the theory, Dr. Siemens supposes 

 the gases which pervade the planetary space to be not only of the same kind as 

 the components of our own atmosphere, which on the kinetic theory of gases 

 must diffuse through that space, but also such gases as are not found in our air, 

 but are found occluded in meteorites, which may be supposed to have acquired 

 them in their previous wanderings. Amongst these he specially mentions hydro- 

 carbons which form the self-luminous part of most comets. It is to these gases, 

 together with aqueous vapour and carbonic acid, that he ascribes the principal part 

 in the conservation of solar energy. That compound gases at the extremely low 

 pressure of the planetary space are decomposed by solar radiation is not inconsistent 

 with the laws of dissociation, for it is quite possible that some compounds may be 

 decomposed at ordinary temperatures by mere reduction of pressure, and the radia- 

 tion absorbed will be the more effective because it will directly affect the vibratory 

 motion within the molecule, and may well produce chemical decomposition before 

 it can, when the free path of the molecules is so much increased by the attenuation 

 of the gas, assume the form of an increased temperatui'e. Dr.Siemens, moreover, 



