+------------------------------------------+ | | Difference between Dry-bulb | | | and Wet-bulb Readings. | |Temperature |-----------------------------| | by the | 2 deg. | 4 deg. | 6 deg. | 8 deg. | 10 deg.| 12 deg.| | Dry Bulb |-----------------------------| |Thermometer.| Degree of Humidity. | |------------------------------------------| | 34 deg. | 79 | 63 | 50 | .. | .. | .. | | 36 | 82 | 66 | 53 | .. | .. | .. | | 38 | 83 | 68 | 56 | 45 | .. | .. | | 40 | 84 | 70 | 58 | 47 | .. | .. | | 42 | 84 | 71 | 59 | 49 | .. | .. | | 44 | 85 | 72 | 60 | 50 | .. | .. | | 46 | 86 | 73 | 61 | 51 | .. | .. | | 48 | 86 | 73 | 62 | 52 | 44 | .. | | 50 | 86 | 74 | 63 | 53 | 45 | .. | | 52 | 86 | 74 | 64 | 54 | 46 | .. | | 54 | 86 | 74 | 64 | 55 | 47 | .. | | 56 | 87 | 75 | 65 | 56 | 48 | .. | | 58 | 87 | 76 | 66 | 57 | 49 | .. | | 60 | 88 | 76 | 66 | 58 | 50 | 43 | | 62 | 88 | 77 | 67 | 58 | 50 | 44 | | 64 | 88 | 77 | 67 | 59 | 51 | 45 | | 66 | 88 | 78 | 68 | 60 | 52 | 45 | | 68 | 88 | 78 | 68 | 60 | 52 | 46 | | 70 | 88 | 78 | 69 | 61 | 53 | 47 | | 72 | 89 | 79 | 69 | 61 | 54 | 48 | | 74 | 89 | 79 | 70 | 62 | 55 | 48 | | 76 | 89 | 79 | 71 | 63 | 55 | 49 | | 78 | 89 | 79 | 71 | 63 | 56 | 50 | | 80 | 90 | 80 | 71 | 63 | 56 | 50 | | 82 | 90 | 80 | 72 | 64 | 57 | 51 | | 84 | 90 | 80 | 72 | 64 | 57 | 51 | | 86 | 90 | 80 | 72 | 64 | 58 | 52 | +------------------------------------------+ The total quantity of aqueous vapour which at any temperature can be diffused in the air being represented by 100, the per-centage of vapour actually present will be found in the table opposite the temperature of the dry thermometer, and under the difference between the dry-bulb and wet-bulb temperatures. The degree of humidity for intermediate temperatures and differences to those given in the table can be easily estimated sufficiently accurately for most practical purposes. The difference between the two thermometer readings taken from the reading of the wet bulb, gives the dew-point very nearly, when the air is at any temperature between freezing and 80 deg. This simple rule will be found serviceable to horticulturists, since it will enable them to estimate the chilling effect of dew or hoar-frost on tender plants. _Use as an Indicator of Weather._--In our climate, the usual difference between the thermometer readings,--in the open air, shaded from the sun, reflected heat, and currents of air,--ranges from one to twelve degrees. In hot and dry climates, as India and Australia, the range out of doors has been found as much as 30 deg., occasionally.