No. 3. Correction due to Latitude 44 No. 4. Correction due to Approximate Elevation 45 Tables for Determining the Temperature of the Vapour of Boiling Water at any Place:-- No. 5. Factor due to Latitude 62 No. 6. Temperature and Tension 62 Table of Temperature of the Soil 69 Table of Difference of Elevation corresponding to a fall of 1 deg. in the Boiling-point of Water 98 Table showing Proportion of Salt for various Boiling Temperatures of Sea-Water 100 Table for finding the Degree of Humidity from Observations with Mason's Hygrometer 108 Table showing Amount and Duration of Rain at London, in 1862 112 Table of Average British Rainfall in Westerly, Central, and Easterly districts 114 Table showing Force of Wind, for use with Lind's Wind-Gauge 118 Tables for Correcting Observations made with-- Brass Hydrometers 142 Glass Hydrometers 143 ADDENDA. PAGE 1. Rule for converting Millimetres into Inches, et vice versa 146 2. Old French Lineal Measure, with English Equivalents 146 3. Rule for finding Diameter of Bore of Barometer Tube 146 4. Wind Scales 147 5. Letters to denote the State of the Weather 147 6. Table of Expansion of Bodies 148 7. Table of Specific Gravity of Bodies 148 8. Important Temperatures 148 9. Table of Meteorological Elements, forming Exponents of the Climate of London 149 10. List of Works on Meteorology 151 METEOROLOGICAL INSTRUMENTS. In the pursuits and investigations of the science of Meteorology, which is essentially a science of observation and experiment, instruments are required for ascertaining, 1. the pressure of the atmosphere at any time or place; 2. the temperature of the air; 3. the absorption and radiation of the sun's heat by the earth's surface; 4. the humidity of the air; 5. the amount and duration of rainfall; 6. the direction, the horizontal pressure, and the velocity of winds; 7. the electric condition of the atmosphere, and the prevalence and activity of ozone. CHAPTER I. INSTRUMENTS FOR ASCERTAINING THE ATMOSPHERIC PRESSURE. [Illustration: Fig. 1.]