The Chief Engineer of the Punjab did not accept the above figures.[19] He remarked that observations taken under great difficulties as to time and place are liable to error, and he considered that an allowance of rainfall at the rate of 4·8 inches per hour--a rate which had been observed elsewhere--and a run-off of ·75 of the fall would be sufficient. He accepted a discharge of 2000 cubic feet per second for catchment areas of less than 5 square miles, assuming the run-off to be ·75 of the fall, but afterwards increased the figure to 2400 cubic feet per second. The chief engineer did not overlook the fact that in the designs for the drainage aqueducts a free-board of 5 feet had been allowed, and perhaps this led to an acceptance of an estimated discharge less than would otherwise have been accepted. It does not seem to be at all certain that the figure put forward by Mr Purves was far wrong. When the original project estimate for the Upper Jhelum Canal was framed, the irrigation engineers had had no experience of small and steep catchments, and no one had suspected that the discharge per square mile would be anything like the above. The sums of money provided for works for the passages of torrents had to be increased in ratios varying from 2·5 to 1 to 6 to 1. The following statement shows the figures for other small catchment areas in the neighbourhood of the Upper Jhelum Canal:-- +----------+------------------+---------+ |Catchment | Discharge per | Run-off.| | Area. | square mile. | | +----------+------------------+---------+ |Sq. miles.| Cub. ft. per sec.| Inches. | | | | | | .79 | 5000 | 7·8 | | 1·47 | 3825 | 5·82 | | 2·96 | 2214 | 3·46 | +----------+------------------+---------+ In the south-east of New South Wales flood discharges of 135 and 84 cubic feet per second have been found for catchment areas of ·91 and 2·5 square miles respectively in broken country. 3. =Rivers.=--It is possible to apply the methods of the preceding article to large catchment areas, but the results would be quite unreliable. If the calculations were made so as to err on the side of safety, the resulting discharges would often be enormous. The following table shows some figures based on actual flood discharges. None of the localities have excessive rainfalls, though most are liable to occasional very heavy falls. In mountainous districts in the North of England and in Scotland the flood discharges per square mile of catchment area have been found to vary from 64 to 320 cubic feet per second.