“It appears clearly that there was a definite tendency for the two-peak cities to fall into two groups in respect of the time elapsing between first and second peaks. About a third of them had the second mortality peak around eight weeks after the first peak. The remaining two-thirds had the second peak, on the average, about thirteen weeks after the first. The three-peak curves had the second peak on an average 7.1 ± 0.3 weeks after the first, and the third peak on an average 13.1 ± 0.3 weeks after the second. The cycle in the epidemic waves would therefore appear to be nearly a multiple of seven weeks rather than the ten weeks tentatively deduced from the dates of peaks. There the process of averaging obscured the true relations.” _Duration of explosive outbreak._—The range of the duration of the first outbreak of epidemic mortality is great, varying from five weeks in Richmond, Virginia, to twenty-three weeks in Atlanta, Georgia. Twenty of the cities, one-half the total number, showed a duration of ten weeks or less, while in the other half the duration was eleven weeks or more. The mean duration of epidemic mortality in the first outbreak was 11.90 ± 0.55 weeks. The ascending limb of mortality rate was rapid in nearly all cities. The descending limb was usually slower. In 34 of the 40 cities it required four weeks or less time for the mortality rate to pass from normal to its epidemic peak. But in only half as many (17) of the cities did the rate come down from its peak to normal again in a period of four weeks or less. The mean time from normal mortality rate to peak was 3.90 ± 0.21 weeks. The mean time from peak mortality rate to normal was 8.00 ± 0.50 weeks. Thus it took about twice as many weeks for the mortality curve to come back from its peak to normal, as were required for the increase from normal to peak at the beginning of the explosion. This is on the average. The ascending limb occupied about a month and the descending limb two months. Pearl’s curves which have been copied in this report (Charts II to VII) enable us to follow his conclusions. Pearl offers a partial explanation for the variations in the different cities. There can be no doubt but what many factors play a role in the causation of these variations, and it is to be regretted that up to the present no statistics for smaller, more homogeneous communities have as yet been reported which could be compared with Pearl’s excellent work on the large cities of the country. Were his work supplemented by records from smaller towns in which the varying factors are less numerous, in which there is less occupational variation, additional conclusions could probably be reached. The unfortunate feature is that as a rule statistics from the smaller cities and towns are less reliable.