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SCIENCE. 



[N. S. Vol. IV. No. 87. 



ficient guide, and refused to burden them 

 with the weight of the theory. Some were 

 engrossed, for the time, in following out 

 practical consequences of the facts; some 

 distrusted conclusions supported by but a 

 single line of evidence; some, perhaps, dis- 

 trusted the capacities of the human mind. 

 But the facts were accepted. 



All scientific men, all sensible men, have 

 a great respect for facts. Perhaps one can- 

 not have too great a respect for facts ; but 

 his respect may be wrongly directed. Facts 

 are often very interesting in themselves ; 

 they often have an important relation to 

 human welfare ; their discovery is often a 

 great intellectual triumph ; and we may re- 

 gard them as the miser regards his gold, 

 forgetting that the most precious use of 

 facts is to help us to see beyond them. 

 Facts are evidence ; but we seek a verdict. 

 Facts are a telescope; we desire enlarge- 

 ment of vision, further insight into nature. 

 Facts are openings which we laboriously 

 hew in the walls which shut us in ; they 

 cost enough to be valuable, but their real 

 value is in that which they promise or dis- 

 close. Facts are a foundation for our build- 

 ing ; the structure must rigorously respect 

 the lines of the foundation ; but it is a pity 

 to believe that the basement walls are the 

 chief beauty desired by the architect or 

 owner. As Tyndall phrased it in a lecture 

 at Manchester, '* Out of experience in sci- 

 ence, there always grows something finer 

 than mere experience. Experience, in fact, 

 only furnishes the soil for plants of higher 

 growth." 



In the present case the soil was fertile, 

 the finer growth has been rapid and vigorous. 

 Dalton inferred that chemical elements con- 

 sist of very small units or individuals ; that 

 all the units or individuals of any given 

 element are equal in weight; and that 

 combination takes place by the groupino- 

 together of different units or individuals. 

 This is Dalton's atomic theory. 



In Dalton's time there was no fact opposed 

 to this novel conclusion ; but there was no 

 second set of facts to support it. The prog- 

 ress of chemistry depended on making- 

 due use of Dalton's three laws, and they 

 were quickly and generally accepted; but 

 whether the hypothetical chemical units or 

 individuals actually exist or not, although 

 a most interesting question, did not press 

 for instant decision. Most chemists re- 

 garded with favor the idea of the actual ex- 

 istence of the chemical units or individ- 

 uals. Dalton called them atoms, and per- 

 haps the name brought misfortune; for 

 many thought that the new theory was, 

 that matter is made up of units or individ- 

 uals which cannot be divided by any possi- 

 ble force. The word ' atom,' the word ' in- 

 divisible,' like the word ' individual,' prop- 

 erly mean that which is not divided in the 

 phenomena considered. An absolutely in- 

 divisible atom, like an irresistible wave or 

 an immovable rock, can be spoken of to 

 puzzle children, but for adults, as Clifford 

 said, " If there is anything which cannot be 

 divided, we cannot know it, because we 

 know nothing about possibilities or impos- 

 sibilities ; only about what has or has not 

 taken place." I judge that many, probably 

 most chemists and physicists understand 

 the word atom correctly : many others un- 

 derstand it to mean that which cannot be 

 divided by any possible force, and so mis- 

 understand it. For instance, the author of 

 the ' History of the Inductive Sciences ' 

 failed to understand the word as chemists 

 and physicists understand it, and so sup- 

 posed that he rejected the atomic theory. 

 Many chemists would reject the theory that 

 matter consists of very small units which 

 cannot be divided. I suppose that very 

 nearly all believe that matter is made up of ■] 

 small units which are not divided in any 

 chemical or physical change yet observed. 

 This is the atomic theory of Dalton. 



A few years after Dalton had formed the 



