BRITISH ASSOCIATIONo 35 



remarkable phenomenon which was seen by independent observers at two diff- 

 erent places on the Ist of September, 1859. A sudden outburst of light, far 

 exceeding the brightness of the sun's surface, was seen to take place, and sweep 

 like a drifting cloud over a portion of the solar face. This was attended with 

 magnetic disturbances of unusual intensity and with exhibitions of aurora of ex- 

 traordinary brilliancy. The identical instant at which the effusion of light was 

 observed was recorded by an abrupt and strongly marked deflection in the self- 

 registering instruments at Kew. The phenomenon as seen was probably only 

 part of what actually took place, for the magnetic storm in the midst of which it 

 occurred commenced before and continued after the event. If conjecture be 

 allowable in such a case, we may suppose that this remarkable event had some 

 connexion with the means by which the sun's heat is renovated. It is a reason- 

 able supposition that the sun was at that time in the act of receiving a more than 

 usual accession of new energy; and the theory which assigns the maintenance of 

 its power to cosmical matter plunging into it with that prodigious velocity which 

 gravitation would impress upon it as it approached to actual contact with the 

 solar orb, would afford an explanation of this sudden exhibition of intensified 

 light in harmony with the knowledge we have now attained that arrested motion 

 is represented by equivalent heat. Telescopic observations will probably add 

 new facts to guide our judgment on this subject, and, taken in connexion with 

 observations on terrestrial magnetism, may enlarge and correct our views re- 

 specting the nature of heat, light and electricity. Much as we have yet to learn 

 respecting these agencies, we know sufficient to infer that they cannot be trans- 

 mitted from the sun to the earth except by communication from particle to par- 

 ticle of intervening matter. Not that I speak of particles in the sense of the 

 atomist. Whatever our views may be of the nature of particles, we must con- 

 ceive them as centres invested with surrounding forces. We have no evidence, 

 either from our senses or otherwise, of these centres being occupied by solid 

 cores of indivisible incompressible matter essentially distinct from force. Dr. 

 Young has shown that even in so dense a body as water, these nuclei, if they 

 exist at all, must be so small in relation to the intervening spaces, iba.t a hundred 

 men distributed at equal distances over the whole surface of England would 

 represent their relative magnitude and distance. What *fien must be these 

 relative dimensions in highly rarefied matter? But why encumber our concep- 

 tions of material forces by this unnecessary imaginings of a central molecule? If 

 we retain the forces and reject the molecule, we sh«l still have every property 

 we can recognize in matter by the use of our sepdes or by the aid of our reason. 

 Viewed in this light, matter is not merely a ^ing subject to force, but is itself 

 composed and constituted of force. 



The dynamical theory of heat is probpSly the most important discovery of the 

 present century. We now know tha*- each Fahrenheit degree of temperature in 

 1 lb. of water is equivalent to a we^^ht of 7721b. lifted 1 foot high, and that these 

 amounts of heat and power are reciprocally convertible into one another. This 

 theory of heat, with its numerical computation, is chiefly due to the labours of 

 May<3r and Joule, though many other names, including those of Thomson and 

 Rankine, are deservedly associated with its development. I speak of this dis- 

 covery as one of the present age because it has been established in our time ; but 



