10 PROGRESS OF HUMAN KNOWLEDGE 



analysis, subtle almost beyond conception, have been 

 furnished collaterally by other sciences. To the spec- 

 trum analysis we owe already four new metals, and the 

 detection of others before known, in combinations un- 

 der which their infinitesimal proportions had hitherto 

 concealed them. The analysis by diffusion and dia- 

 lytic separation, due to the researches of Mr. Graham, 

 is another of these new methods, the more inte- 

 resting from its direct relation to the atomic consti- 

 tution and molecular changes of matter. 



Electricity, though still a mystery in certain of its 

 most elementary facts, has- been a field for the highest 

 refinements of experimental research ; illustrating by 

 wonderful results the new and mighty power now sub- 

 mitted to the will and uses of man. Heat, as one of 

 the great motive forces of the universe, has been simi- 

 larly the subject of experiment, creating what might be 

 called a science in itself, were it not so closely linked 

 with other phenomena of the natural world. Light, 

 that sister ' offspring of heaven,' has afforded to man 

 one of his greatest triumphs, through those beautiful 

 experimental researches, aided by the higher mathema- 

 tics, which have disclosed to us the sunbeam as the most 

 marvellous object in the natural world, and carried 

 our knowledge yet beyond, to the sun itself to its ele- 

 ments and unceasing changes of state. All parts of 

 physical science yield similar if less striking illustra- 

 tions. All are so connected by physical relation of 

 matter and force, that a successful experiment in one 

 science often discloses the secrets of another seemingly 

 far removed. 



