--------------+------------+-------------+-------------+------------- | Shown by | Within Ten | 11 to 20 | More than | Record |Minutes after|Minutes after| Twenty | Sheets. | Washing. | Washing. |Minutes after | | | | Washing. --------------+------------+-------------+-------------+------------- WARREN FILTER.| | | | February | 115 | | 118 | 114 March | 316 | 50 | 515 | 301 April | 79 | 417 | 207 | 75 May | (Special experiments, omitted.) June | 197 | 493 | 272 | 170 July | 300 | | 546 | 207 August | 174 | 356 | 601 | 223 | | | | JEWELL FILTER.| | | | February | 2453 | 2425 | | 2099 March | 455 | 657 | 958 | 354 April | 99 | 665 | 462 | 165 May | 144 | 998 | 346 | 127 June | (Special experiments, omitted.) July | 279 | 1330 | 272 | 274 August | 344 | 612 | 323 | 376 --------------+------------+-------------+-------------+------------- The time of inferior work very rarely exceeded twenty minutes. It will be seen from the tables that the results as shown by the record sheets are never very much higher, and are occasionally lower than the results of samples taken on corresponding days more than twenty minutes after washing; and thus while a decrease in bacterial efficiency was noted after washing, no material increase in the average bacterial efficiency of the mechanical filters would have been obtained if these results had been excluded. The results for the whole time would be affected much less than is indicated by the table, because the table includes only results of those days when samples were taken just after washing, while the much larger number of days when no such samples were taken would show no change whatever.