vi PREFACE 



occurred in different places, so that it was possible to con- 

 struct almost entirely in the author's own words a fairly 

 consistent whole. Although these fragments were not deemed 

 worthy of publication by their author, and although doubt- 

 less he would have preferred to revise them before printing, 

 it has seemed worth while to publish them because they 

 formed one of the very first presentations of the new phys- 

 ical chemistry on this side of the Atlantic. 



The popular address on "Atoms and Molecules " also was 

 found in manuscript, and like the preceding essay, has had 

 incorporated into it several scattered paragraphs upon the 

 same subject from other incomplete notes. Thus it is hoped 

 that all of his written work on this subject that is worthy 

 of printing has been preserved in readable form. 



Another paper printed for the first time is that on Sir 

 Isaac Newton, which is of interest in showing the author's 

 appreciation of the value of abstract scientific research. 



The only other important paper found in manuscript 

 (placed under the title " Chemistry and Civilization," at the 

 end of the first group of papers) was intended by Professor 

 Loeb to be the introduction to a proposed comprehensive book 

 upon the usefulness of the science in its widest sense. Upon 

 this book he was working at the time of his death ; and one 

 cannot but poignantly regret, after reading the introductory 

 chapter, that the completion of the project was denied him. 



Two of the researches included in the second group were 

 published both in German and in English; in these cases both 

 versions are reprinted, because the translations are evidently 

 the author's work, and differ in several details from the 

 originals. 



In each of the scientific articles included in the second 

 part of the book, the page numbers of the original publica- 

 tion are inserted in brackets at the proper places, to show 



