CHAPTERLXIX.MENSURATION OF HEIGHTS.Rules for calculating Heights by Means of the Barometer and Thermometers.Section 348.RULES for calculating the Height of Mountains, when applied to those elevated Stations in the Atmosphereattainableonly by Means of the Balloon, will henceforward become more useful, and be more frequently practised: as the Lives of Aironautsmaydepend on a Knowledge of theirHeightabove the Earth; which, not being determinable bySight, inall Weathers, or at all Times, must be referred to theBarometerandThermometers, they carry up with them.De Luc, Horseley, Maskelyne, Shuckburgh, and Roy, have each writtenablyon the Subject, in theTransactions: tho’ few have either Leisure or Inclination to follow them.Sir George Shuckburgh has made successful Attempts to smooth the Way, by Examples and Tables, yet is still too concise for actual Learners, and the Generality of those who will have Spirit enough to go before the Calculators in exploring the Atmosphere; but cannot dedicate sufficient Leisure to overtake them in their Studies.Each may therefore assist the other.349. Whoever is at the Trouble of comparing the Observations made by Shuckburgh, with the Directions here given, will find that the latter contains theEssentialsof the former, with this material Difference, that the Investigation moveshere by Steps, which are all pointed out to the Learner; and not by Strides.Each Step is self evident: and, by carrying Conviction to the Mind, is just what the Mind itself woud make use of, in the Attainment of anydistantTruth.To do every Justice to Sir George, the Merit of whose Performance wants no Eulogium; his three Precepts are copied; tho’ rather as a Memorandum for those who understand the Methods; than as plain Directions for such as are yet to learn them.It will be found likewise, that the first, second, and fourth Tables are greatly enlarged: being calculated for thoseextremeTemperatures, and Heights, which the Balloononlycan attempt to reach: and the fourth Table, for greater Dispatch in computing the Expansion of the Air.The Foundation and Construction of each Table, is also methodically traced and elucidated.
CHAPTERLXIX.
Rules for calculating Heights by Means of the Barometer and Thermometers.
Section 348.RULES for calculating the Height of Mountains, when applied to those elevated Stations in the Atmosphereattainableonly by Means of the Balloon, will henceforward become more useful, and be more frequently practised: as the Lives of Aironautsmaydepend on a Knowledge of theirHeightabove the Earth; which, not being determinable bySight, inall Weathers, or at all Times, must be referred to theBarometerandThermometers, they carry up with them.
De Luc, Horseley, Maskelyne, Shuckburgh, and Roy, have each writtenablyon the Subject, in theTransactions: tho’ few have either Leisure or Inclination to follow them.
Sir George Shuckburgh has made successful Attempts to smooth the Way, by Examples and Tables, yet is still too concise for actual Learners, and the Generality of those who will have Spirit enough to go before the Calculators in exploring the Atmosphere; but cannot dedicate sufficient Leisure to overtake them in their Studies.
Each may therefore assist the other.
349. Whoever is at the Trouble of comparing the Observations made by Shuckburgh, with the Directions here given, will find that the latter contains theEssentialsof the former, with this material Difference, that the Investigation moveshere by Steps, which are all pointed out to the Learner; and not by Strides.
Each Step is self evident: and, by carrying Conviction to the Mind, is just what the Mind itself woud make use of, in the Attainment of anydistantTruth.
To do every Justice to Sir George, the Merit of whose Performance wants no Eulogium; his three Precepts are copied; tho’ rather as a Memorandum for those who understand the Methods; than as plain Directions for such as are yet to learn them.
It will be found likewise, that the first, second, and fourth Tables are greatly enlarged: being calculated for thoseextremeTemperatures, and Heights, which the Balloononlycan attempt to reach: and the fourth Table, for greater Dispatch in computing the Expansion of the Air.
The Foundation and Construction of each Table, is also methodically traced and elucidated.