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if in practice it be found untenable — in other words, if on the 

 application of a test it is found wanting. In the physical world 

 no better illustration of a theory and of its practical application 

 can be adduced than that set up by a fellow-Cumbrian, Dalton, 

 and which remains till the present time unshaken as a "reasonable 

 explanation of phenomena." The view propounded by Dalton 

 was that matter exists in the form of atoms of different sizes which, 

 when grouped together, unite in certain definite mathematical 

 proportions, the proportions being always constant; that these 

 atoms are the limits to which matter can be subdivided, and are 

 so minute as to defy any examination. This theory, involving the 

 three laws of chemical combination, is supported by facts which 

 bear upon it indirectly. There is no direct evidence of its truth, 

 as no one has ever seen an atom, and in point of fact their 

 existence is purely theoretical. But what is the value of the 

 theory? Briefly this — that the whole practice of modern chemistry 

 has hinged upon it, and it remains the rule by which the operations 

 of an important branch of science may be safely guided. Such a 

 theory as this may be spoken of as established, yet it is but a 

 theory, and may never in human experience be raised out of that 

 position into one of actual fact. This may serve as an example of 

 many other physical theories, which being reasonable explanations 

 of phenomena, daily receive practical application, the laws which 

 govern the physical operations and which are involved in the 

 theory being brought into action. In such theories and their 

 application, we see the relation which is pointed out by Mr. 

 Kendall as that of thinking and' doing, but which is yet a broader 

 one than is quite conveyed to the mind by these terms. Such a 

 relation is close enough, and in it we may admit the proposition 

 that " theory and practice are reciprocal parts of a unity." Doubt- 

 less there is a class of theories which can never be practically 

 appUed, though their influence may be none the less great in 

 directing us towards the solution of problems which may beset the 

 mind. The ceaseless spirit of inquiry has in all ages led to the 

 foundation of speculations as to the origin of the universe and 

 its destiny. These speculations have through the more recent 



