extensive papers for the British Association, that he had 
Bot been able to prepare a paper of interest, but as president 
of the section he would make a few introductory remarks 
upon " Solar power, radiations and emanations." Sir Isaac 
Newton had demonstrated that by refraction he could pro- 
duce from white light a prismatic spectrum, composed of 
seven primary colours of different refrangibilities, and that 
these seven primary colours could be re-combined to produce 
white light. Sir David Brewster had shown that these 
rays were capable of absorption by different substances, 
and assumed that only three primary mono-chromatic 
colours existed. When any substance was looked at 
by a pure yellow mono-chromatic light, all the coloured 
rays but the yellow being absent, only the yellow 
ray could be reflected; so that all bodies were then 
either decidedly yellow or black, whatever their colour 
may appear to be in ordinary white light. On the contrarj', 
when seen by red light, the red only was reflected, and 
when seen by blue light, the blue was reflected, all other 
rays being absent; other coloured objects would appear 
black of various depths of shade. So that he considered the 
' solar spectrum to consist of three spectra— the red, yellow, 
and blue placed one over the other, and he thought that these 
were the only primary colours. This idea of the constitution 
of the solar spectrum has lately received some severe blows. 
The new metal thallium gives a beautiful mono-chromatic 
green light, which cannot be split or analysed by re- 
fraction or absorption, and we must therefore admit the 
' colour of the flame of thallium to be a primary or mono- 
chromatic colour equally with the sodium yellow. The re- 
searches of Herschel and Stokes prove the spectrum to be 
still more complicated. Stokes showed that there is bevond 
the extreme violet ray an invisible spectrum, containing as 
many rays and dark bands as the ordinary visible spectrum, 
and which could be made visible by the changes produced 
on papers prepared with quinine, quinidin, turmerie, or 
esculine, &c., on which the solar spectrum was thrown. 
These facts lead us to extend our notion of prismatic analysis, 
and to consider that there are at least seven primary 
colours or probably more. Heat and chemical agency also 
accompany the rays of liG;ht and constitute part of the solar 
i radiations. These different rays can be separated by 
I passing through various substances. Thus solutions of 
quinine or quinidin will arrest and reflect the extreme 
or ultra-violet rays of lighr, and render visible the 
florescent rays, giving a beautiful blue colour. A plate of 
alum or ice, one tenth of an inch thick, will absorb all the 
rays of heat ; a plate of yellow glass will absorb and arrest 
all chemical power, whilst a plate of blue glass will cut off 
the maximum amount of illuminating power, but will trans- 
mit the actinic, chemical, or photographic rays, so that th« 
solar spectrum consists of three agencies—light, beat, and 
chemical power. Solar heat is the cause of the magnetism 
of the earth, by producing electrical phenomena or currents 
in the atmosphere at ri^-ht angles to the poles. We mpy also 
say that the population of the earth is due to solar agency, 
through the ultimate 'conversion of coal into man. Many 
believe that all men have sprung from one common ancestor, 
but according to other authorities the human race has arisen 
' from five widely separated centres. E^ch adult human 
being contains 21 lb. weii,'ht of carbon in his body. There 
are now more than 1000 millions of inhabitants in the 
various nations of the world. Whence comes all the car- 
bon contained in the bodies of the human race? It is r.ot 
handed down from father to son. The infant of scarcfly 
nine pounds' weight represents about 1^ lb. of carbon. There 
are at the present day more than 9^ millions of tons of car- 
bon invested in the bodies of the human race. Now, coal 
burnt in our factories or on the household hearth becomes 
carbonic acid; this carbonic acid is decomposed by veL'etables, 
the carbon being absorbed through the agency of light and 
solar heat; the vegetables become the food of animals, and 
animals and vegetables are the food of man— so that we mav 
