Sudbury | 75.2 |1875-97|22.98|17.52|76.0|22.61| 4.70|20.8 Cochituate | 18.87|1863-96|22.97|14.87|64.7|24.10| 5.46|22.7 Mystic | 26.9 |1878-96|22.11|15.12|68.4|21.66| 4.84|22.4 Connecticut |10,234 |1871-85|20.13|17.95|89.1|24.56| 7.30|29.7 Croton | 338 |1870-94|23.39|17.81|76.1|24.99| 6.76|27.0 Upper Hudson | 4,500 |1888-96|18.20|16.23|89.0|21.50| 7.13|33.0 Genesee | 1,060 |1894-96|19.58|10.20|52.2|20.24| 2.75|13.6 Passaic | 822 |1877-93|22.47|18.22|81.1|24.39| 7.19|29.5 -----------------+---------+-------+-----+-----+----+-----+-----+---- The information to be drawn from this table is sufficient to give clear and general relations between the recorded precipitation and run-off. The percentage of run-off is seen to vary quite widely, but as a rule it is materially less for the year of minimum flow than for the average year. That feature of the table is an expression of the general law, other things being equal, that the smaller the precipitation the less will be the percentage of run-off. A number of influences act to produce that result. During a year of great precipitation the earth is more nearly saturated the greater part of the time, and hence when rain falls less of it will percolate into the ground and more of it will run off. Again, if the ground is absolutely dry, a certain amount of rain would have to fall before any run-off would take place. The area and shape of a watershed will also affect to some extent the flow of the stream which drains it. A larger run-off would reasonably be expected from a long narrow watershed than from one more nearly circular in outline. The greater the massing of the watershed, so to speak, the more opportunity there is for the water to be held by the ground and the less would be the run-off. TABLE VIII. AVERAGE YIELD OF SUDBURY WATERSHED, 1875-1899, INCLUSIVE, VARIOUSLY EXPRESSED.