38 THE PROGRESS AND SPIRIT OF 



chemists) first gave clear declaration to the principle ; and 

 illustrated its applications, mighty in their universality, with 

 a simple sagacity belonging to the genius and habits of the 

 man. The simplicity of his early experiments is, indeed, 

 characteristic also of the manner in which many of the 

 highest truths in science have been reached. Facts the most 

 familiar to common observation, and thence disregarded by 

 common intellects, have furnished better materials and sug- 

 gestions for discovery than the most recondite theories. 



It has been justly said by Sir J. Herschel that number, 

 weight, and measure are the foundations of all exact science. 

 The atomic doctrine has acquired from chemistry these con- 

 ditions, which give it substance and certainty as a physical 

 truth. When analysis and synthesis, carefully applied to 

 compound bodies, disclosed a constant and definite propor- 

 tion of the combining elements, and an equivalent or multiple 

 ratio of parts in every chemical change, the requirements of 

 number, and weight, and measure were all met and satisfied 

 by the discovery. 



Here then we have a great law, or group of laws, 

 thoroughly attested ; of high generality ; and proving, 

 because based upon it, that atomic or molecular constitution 

 of matter which alone could afford such results. Whatever 

 name we give to them, these atomic parts exist in all bodies, 

 and determine by their own nature or arrangement the 

 properties and functions of each. That they are minute 

 beyond all human measure is proved, not only by the 

 chemical relations just denoted, but also by those relations 

 to heat, light, electricity, and mechanical force which ex- 

 periment has demonstrated. No hindrance, indeed, to belief 

 need exist on this score. Matter, either unorganised as we 

 term it, or organised into life, affords endless examples of 

 a divisibility, which we seek to put before the eye in figures, 

 but which no human sense can follow or conceive. While, 



