244 THE WONDERFUL CENTURY. CHAP. xvm. 



which may be added certain classes of official evidence 

 serving as test cases or " control experiments " on a large 

 scale. Almost the whole of the evidence will be derived 

 from the Reports of the recent Royal Commission. 



In determining what statistics really mean the graphic 

 is the only scientific method, since, except in a few very 

 simple cases, long tables of figures are confusing; and if 

 divided up and averages taken, as is often done, they can 

 be manipulated so as to conceal their real teaching. 

 Diagrams, on the other hand, enable us to see the whole 

 bearing of the variations that occur, while for compari- 

 son of one set of figures with another their superiority 

 is overwhelming. This is especially the case with the 

 statistics of epidemics and of general mortality, because 

 the variations are so irregular and often so large as to 

 render tables of figures very puzzling, while any just 

 comparison of several tables with each other becomes 

 impossible. I shall therefore put all the statistics I have 

 to lay before my readers in the form of diagrams, which, 

 I believe, with a little explanation, will enable anyone to 

 grasp the main points of the argument. (See end of 

 volume.) 



London Mortality and Small-pox. 



The first and largest of the diagrams illustrating tiiis 

 question is that exhibiting the mortality of London from 

 the year 1760 down to the present day (see end of vol- 

 ume). It is divided into two portions, that from 1760 

 to 1834 being derived from the old " Bills of Mortality," 

 that from 1838 to 1896 from the Reports of the Regis- 

 trar-General. 



The " Bills of Mortality " are the only material avail- 



