INTRODUCTION ix 



There were also many practical applications in the field of electronics and 

 radio engineering. 



It has been the experience of our laboratory that the search for knowl- 

 edge in new fields by those who are alert to the possible applications, 

 frequently leads to new discoveries. The word, serendipity, coined two 

 centuries ago by Horace Walpole, well describes this situation. Serendipity 

 may be defined as "the art of profiting from unexpected occurrences." 

 Much of the progress, not only in research laboratories but in the world 

 as a whole, depends on serendipity rather than on careful planning directed 

 toward specific ends. Many of the chapters of this volume afiford examples 

 of serendipity. 



The study of the chemical reactions taking place in contact with heated 

 tungsten filaments in gases at low pressures led to an interest in the 

 mechanism underlying these chemical reactions. The dissociation of hydro- 

 gen molecules into atoms involved a great deal of heat absorption. One of 

 the b.est ways of studying this was to measure the energy necessary to 

 maintain a tungsten wire at a very high temperature in the presence of 

 hydrogen. This was the basis of the work of "Flames of Atomic Hydrogen" 

 given in Chapter Eight, which received application as a new method of 

 welding metals. 



The work on surface chemistry (in field G) started from the study of 

 the reactions on solid surfaces and the catalysis involved in the mechanisms 

 of these reactions (field B). It was soon found that most of these phe- 

 nomena depended upon the presence of a single layer of atoms. This was 

 a new factor which had not been previously considered in connection with 

 the structure of matter. There are many papers, therefore, that deal with 

 the structure of matter in general (field B) and more particularly with the 

 structure of surfaces. In order to find if these relationships were general, 

 work was started with the surfaces of liquids and this gradually led to the 

 stud}^ of surface tension and monomolecular films on water and on other 

 liquids. This science of surface chemistry is gradually leading to biological 

 applications. The field "H" given in the bibliography, which includes 

 meteorology, originated from my early enthusiasm for mountain climbing 

 (1893) and skiing (1903). Work during the first World War on sub- 

 marine detection aroused my interest in the motion of water, particularly 

 as influenced by the efifect of wind acting on the surface. This led to studies 

 of the motion of water in rivers and lakes, which later proved useful in 

 connection with war work on smokes and the icing of aircraft. 



It has often been said that during war the energies of scientists are 

 taken away from the fields of pure science and are devoted merely to 

 applications. My own opinion is that both world wars have greatly stimu- 

 lated even pure science by bringing scientists in contact with much wider 



