Preface \ii 



however limited ;i decree, tend in the future to lighten i h<- l.ibour of men of 



the energy spent <>n UK: computing ;ind illustrating of the tables will not have been 



WiUStcd. 



In the revision of the Introduction to Part I, I ha<l the able and unselfish h-|p of 

 my then colleagues II. E. Soper and Ethel M. Klderton. The former, sadly for our 

 science, has passed to the place where either no problems exist, or th:ir solution* 

 are clear as day. Who can venture to say which? For the proofs of the present 

 Introduction I have had most generous aid from iny friends and colleagues 

 Ethel M. Elderton, Egon S. Pearson, E. C. Fieller and Brenda N. Stoessiger. I 

 am the more deeply indebted to them as they have spent much time in checking 

 the numerical illustrations, in many of which they have corrected faults in my 

 arithmetic, which would, if left undiscovered, certainly have detracted greatly from 

 the value of this book. I owe to them also many suggestions for making more 

 lucid my presentation of methods for conducting the calculations, and often for 

 apt changes in the language I had used. The diagrams are mainly due to my 

 former colleague Miss Ida M c Learn (now Mrs F. Larmor), to whom I am greatly 

 indebted also for the preparation of the table of powers, lithographed for this 

 work. 



Lastly I have to thank the Council of the Royal Society for permission to 

 reproduce my chart of the $1, /3 a distribution, which indicates the areas and contours 

 to which the various types of frequency curves are appropriate, and further the 

 Council of the Cambridge Philosophical Society for leave to republish Glaisher's 



table of Inverse Factorials. 



KARL PEARSON. 



