--+----------------+---------------+-----------+----------------+-- | Date. | Level of Lake.| Fall in | Daily Average. | | | R.L. | 30 Days. | | +----------------+---------------+-----------+----------------+ |1st June, 1889 | - 41·63 | | | | | | | | |1st July „ | - 41·87 | ·24 | ·008 | | | | | | |31st July „ | - 42·11 | ·24 | ·008 | | | | | | |1st June, 1890 | - 42·38 | | | | | | | | |1st July „ | - 42·66 | ·28 | ·0093 | | | | | | |31st July „ | - 42·89 | ·24 | ·008 | --+----------------+---------------+-----------+----------------+-- The evaporation, then, could not have been less than ·0093 of a metre per diem in June 1890; or less than ·008 per diem in June and July 1889 and July 1890. Allowing for a slight amount of drainage finding its way into the lake, an estimate of 1 centimetre a day for evaporation during the three hottest months of the summer would seem to be nearly correct. We have also the following figures:— R.L. On 14th March, 1890, the lake level was - 42·00 On 18th September, 1890 „ - 43·13 ----- The fall in 188 days was therefore 1·13 ----- Giving a daily average of ·006 As, for half this period, the flow of water into the lake must have been considerable, the average fall per diem due to evaporation for these six months must have been certainly over 6 millimetres. Observations on evaporation made in the Abassieh Observatory in Cairo give the following figures as the measure of the average evaporation for each month of the year:— Metres. January ·071 February ·074 March ·172 April ·193 May ·252 June ·299 } } Average per diem July ·370 } for three hottest } months, ·0107. August ·310 } September ·226 October ·179 November ·120 December ·098 ----- Total 2·364 metres per annum.