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 comparisons 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 any one to grasp the main points of the argument. LONDON MORTALITY AND SMALL-POX The first and largest of the diagrams illustrating this question is that exhibiting the mortality of London from the year 1760 down to the present day (see end of volume). It is divided into two portions, that from 1750 to 1834 being derived from the old “Bills of Mortality,” that from 1838 to 1896 from the Reports of the Registrar-General. The “Bills of Mortality” are the only material available for the first period, and they are far inferior in accuracy to the modern registration, but they are probably of a fairly uniform character throughout, and may therefore be as useful for purposes of comparison as if they were more minutely accurate. It is admitted that they did not include the whole of the deaths, and the death-rates calculated from the estimated population will therefore be too low as compared with those of the Registrar-General, but the _course_ of each death rate—its various risings or fallings—will probably be nearly true.[7] The years are given along the bottom of the diagram, and the deaths per million living are indicated at the two ends and in the centre, the last four years of the Bills of Mortality being omitted because they are considered to be especially inaccurate. The upper line gives the total death-rate from all causes, the middle line the death-rate from the chief zymotic diseases—measles, scarlet-fever, diphtheria, whooping-cough and, fevers generally, excluding small-pox, and the lower line small-pox only. The same diseases, as nearly as they can be identified in the Bills of Mortality according to Dr. Creighton, are given in the earlier portion of the diagram from the figures given in his great work, _A History of Epidemics in Britain_. With the exception of these zymotics the diagram is the same as that presented to the Royal Commission (3rd Report, diagram J.), but it is carried back to an earlier date.