Ixii REPORT — 18GG. 



matter with which wo nro acquainted capable of manifesting all these modes 

 of force, but so-called matter supposed incapable of such manifestations would 

 to most minds cease to be matter. 



Fiu'tlicr than this it seems to me (though, as I have taken an active part 

 for many years, now dating from a quarter of a century, in promoting this 

 ^dcw, I may not be considered an imptu'tial judge) that it is now proved tliat 

 all these forces are so invariably connected inter se and with motion as to be 

 regarded as modifications of each other, and as resolving themselves objec- 

 tively into motion, and subjectively into that something which produces 

 or resists motion, and which we call force. 



I may perhaps be permitted to rccal a forgotten experiment, which 

 nearly a quarter of a century ago I showed at the London Institution, an 

 experiment simple enough in itself, but which then seemed to me important 

 from the consequences to be deduced from it, and the importance of which 

 will be nrach better appreciated now than then. 



A train of multiplying wheels ended "with a small metallic wheel which, 

 when the train was put in motion, revolved with extreme rapidity against the 

 periphery of the next wheel, a wooden one. In the metallic wheel was 

 pliiced a small piece of phosphorus, and as long as the wheels revolved, the 

 pliosphorus remained unchanged, but the moment the last wheel was stopped 

 by moving a small lever attached to it, the phosphorus biirst into flame. 

 Mj object was to show that while motion of the mass continued, heat Avas 

 not generated, but that when this was arrested, the force continuing to ope- 

 rate, the motion of tlie mass became heat in the particles. The experiment 

 ditfcred from that of llumford's eannon-boring and Davy's friction of ice in 

 showing that there was no heat while the motion was unresisted, but that the 

 heat was in some way dependent on the motion being impeded or arrested. 

 We have now become so accustomed to this Aiew, that whenever we find 

 motion resisted we look to heat, electricity, or some other force as the 

 necessary and inevitable result. 



It would be out of place here, and treating of matters too familiar to the 

 bulk of ray aiidience, to trace how, by tlie labours of Oersted, Scebeck, Faraday, 

 Talbot, Dagucrre, and otliers, materials have been provided for the generaliza- 

 tion now laioAvn as the correlation of forces or conservation of energy, while 

 Davy, Eumford, Bcguin, Mayer, Joule, Helmlioltz, Thomson, and others 

 (among whom I woidd not name myself, were it not that I may be misimdcr- 

 stood and supposed to have abandoned all claim to a share in the initiation 

 of this, as I believe, important generalization) have carried on the work; 

 and how, sometimes by independent and, as is commonly the ease, nearly 

 simultaneous deductions, sometimes by progressive and accumidated disco- 

 A-erics, the doctrine of the reciprocal interaction, of the quantitative relation, 

 and of the necessary dependence of all the forces has, I think I may venture 

 to say, been established. 



If magnetism, be, as it is proved to be, connected with the other forces or 

 affections of matter, if electrical currents always pi'oduce, as thej- are proved 

 to do, lines of magnetic force at right angles to their lines of action, mag- 

 netism must be cosmical, for where there is heat and light, there is electricity 

 and consequently magnetism. Magnetism, then, must be cosmical and not 

 merely terrestrial. Could we trace magnetism in other planets and suns as a 

 force manifested in axial or meridional lines, l. e. in lines cutting at right 

 angles the curves formed by their rotation round an axis, it would be a great 

 step ; but it is one hitlierto unaccomplished. The apparent coincidences be- 

 tween the maxima and minima of solar spots, and the decennial or undecen- 



