666 HISTORY OF SCIENCE. 



and was born at Belfast in 1824, and graduated at Cambridge as se- 

 cond wrangler in 1845. The following year he was appointed Pro- 

 fessor of Natural Philosophy in the University of Glasgow, and he still 

 occupies that position. He has published many physico-mathematical 

 papers on electricity, elasticity, the rigidity of the earth, and other 

 subjects; and, in fact, in many departments of science, his extraordi- 

 nary mathematical insight has been of the highest service. It is to 

 his profound researches and elegant instrumental contrivances that the 

 success of the submarine telegraph is mainly owing. On the comple- 

 tion of the Atlantic Cable in 1866, he received the honour of knight- 

 hood, and many marks of academical distinction have also been con- 

 ferred upon him. Of all Thomson's investigations those relating to 

 heat and energy are the most remarkable. He has shown that in all 

 the transformations of energy, although in the strict sense there is no 

 loss, yet a portion of the energy takes a form in which it is. so far as 

 we know, no longer available for reproduction into other forms. For 

 example, of the total heat supplied to a steam-engine, only a small 

 fraction is converted into work, the rest being radiated or conducted 

 away, part of the work reappearing as heat in the friction of the bearings 

 of the machine. The heat thus lost without any useful effect is ulti- 

 mately radiated into space. Now there is no known process by which 

 the low-temperature heat thus diffused is ever again stored up in any 

 form available as a source of energy. The quantity of heat thus dif- 

 fused, if gathered up into a source of high temperature, would be ready 

 for transmutation into work, electricity, etc. ; but, so far as we know, 

 it is in its diffused state like so much water which has descended from 

 a height to the sea-level. This principle, which has been termed the 

 dissipation of 'energy r , asserts, then, that the energy of the universe is 

 flowing down, as it were, from a higher to a lower level, and that 

 throughout its varied manifestations, as heat, electricity, motion, che- 

 mical affinity, vital actions, etc., this constant degradation, which will 

 ultimately bring all to the dead level of a uniformly diffused tempera- 

 ture, is in operation. This speculation leads to a result exactly the 

 opposite to that of Hutton (page 413), for a process of degradation 

 cannot be eternal. All the forces in our planet may be traced to 

 energy now or in times past derived from the sun ; and it is part of 

 the general doctrine of the conservation of energy that the sun's light 

 and heat are maintained by condensation of his material, by aero- 

 lites attracted into his mass, or in some similar manner the process 

 being one in which a state of equilibrium must at length be reached, 

 and the sun himself become a dark rayless mass. 



The whole tendency of scientific investigation is therefore to sub-? 

 stitute a dynamical view of the universe for a static one. We are no 

 longer permitted to look for stability and eternal endurance in any 

 region of the visible world. Atoms and planets are alike in unceasing 

 motion, but never twice traverse the same space. On our own habi- 



