Note 1 — V
Reading edition
In 1867 the difference between the highest and lowest barometrical readings was not more than 13.96 millimetres, and would have been much less if the mercury had not been much depressed by storms in July and September. The hourly variations amounted to very few millimeters. Daily reading of the barometer.—The mercury rises in the early morning till about 9 a.m., it then falls up to 3 or 4 p.m., from then it rises again till 9 p.m., and then again falls till towards day-break. Both the principal atmospheric currents prevalent in Manila exercise a great influence over the mercury in the barometer; the northern current causes it to rise (to an average height of 756 millimeters), the southern causes it to fall (to about 753 millimeters). Temperature.—The heat increases from January till the end of May, and then decreases till December. Average yearly temperature, 27.9° C. The highest temperature ever recorded (on the 15th of April at 3 p.m.) was 37.7° C.; the lowest (on the 14th of December and on the 30th of January at 6 a.m.), 19.4° C. Difference, 18.3° C.1 Thermometrical variations.—The differences between the highest and lowest readings of the thermometer were, in January, 13.9°; in February, 14.2°; in March, 15°; in April, 14.6°; in May, 11.1°; in June, 9.9°; in July, 9°; in August, 9°; in September, 10°; in October, 11.9°; in November, 11.8°; and in December, 11.7°. Coolest months.—November, December and January, with northerly winds. Hottest months.—April and May. Their high temperature is caused by the change of monsoon from the north-east to the south-west. The state of the temperature is most normal from June to September; the variations are least marked during this period owing to the uninterrupted rainfall and the clouded atmosphere. Daily variations of the thermometer.—The coolest portion of the day is from 6 to 7 a.m.; the heat gradually increases, reaches its maximum about 2 or 3 p.m., and then again gradually decreases. During some hours of the night the temperature remains unchanged, but towards morning it falls rapidly.