CHAPTERLVI.NEW MODE OF ASCENT, TO DETERMINE THE INSTANT THE BALLOON IS ARRIVED AT ANY GIVEN HEIGHT: TO MEASURE THE HEIGHTS: AND TO ESTIMATE THE DENSITIES OF THE AIR AT THE GIVEN HEIGHTS.ALSO, A METHOD OF ASCENDING TO A FIXED BAROMETRIC HEIGHT: THERE TO REMAIN SUSPENDED IN EQUILIBRIO.Section 299.PREVIOUS to the Ascent, provide a Cord, which shall have sufficient Strength to support twice its own Weight, when so great a Quantity of it iscoiledtogether, as, if extended, woud measure half a Mile or a Mile.Weigh the wholeCoil, or any Number of Yards, so as to obtain the whole Weight.Mark the whole Length of the Cord, with differentcolouredWorsted, or otherways, at the Distance of every eight Yards: as asoundingLine.Note the Marks in a Pocket-Book.These Things being done; give the Balloon, byinflation, a Power of Levityat leastequal to the known Weight of the Cord: which may be easily obtained by throwing into the Car, alreadyballastedand prepared, a Weight equal tothe Aironaut, together with that of theCord.The Cord must also, previous to the Ascent, be rolled upon a Reel, (made fast in the Ground) whose Diameter shoud betwoFeet: each Turn of the Wheel may be called two Yards.A Barometer with an attached Thermometer fixed in the same Frame, also a second or detached Thermometer placed at the Distance of a Yard from the Frame, shoud remain upon the Ground during the Inflation.The same Apparatus of Barometer with attached and detached Thermometer, shoud be suspended in the Car.The Instant the Balloon ascends, an Observer below is to note in a Book thePointat which the Quicksilver stands in each of thethreeTubes of the lower Apparatus, also the Time of Ascent: the Aironaut the same.The Rope is, previous to the Ascent, to be tyed to a Center above the Car: and as soon as the Balloon has elevated the Car 100 Yards; the Observations, as before, are to be set down below, and by the Aironaut: and repeated at the Height of each 100 Yards: a Drum to beat; during the Time each Observationbelowisnotingdown; and the Balloon not suffered to rise, till the Drum has ceased. By such repeatedNotice, andSilence; the Aironaut will know theexact Height, at which the Balloon is checked in its Elevation: and theexact Timeduring which its Elevation is impeded.This Process is to continue, till the Rope is raised to its full Length.At which Instant a double-barrel Gun is tobe fired: the exact Time notedbelow: and the Time of hearing the Sound noted above.These Notes are to be compared at the Aironaut’s arrival on Earth.300. For suchniceExperiments the Aironaut shoud ascend half an Hour beforesunrise, orSunset: and the Day chosen by the foregoing Rules.The Air must bequite calm: but it is not necessary that it shoud be free from Clouds or Mist.When the Rope is at its full Extent, the Operatorbelowis to shorten it, by winding down the Balloon, 100 Yards: the Signalsbelow, being repeated, till the Balloon is arrived within 100 Yards of the Ground.To estimate the Densities at different Heights.301. While one Observerbelowis writing down the Observation to be made the Instant the Balloon has risen exactly 100 Yards; another Operator is to weigh, by Hand, with Spring Steel-Yards, the Force of Levity already acquired, which is to be noted down by a third Bystander.This Process is to be repeated at every 100 Yards.The Levity, it is true, will encrease as the Balloon rises, (probably in a geometric Progression;)â [100]yet the Cord, by rising with the Balloon, will greatly check it: if, however, it proveinsufficient for that Purpose, and, lest the Cord shoud be in Danger of breaking; the Bottom of the Balloon must be opened, or the upper Valve drawn.If theCord,Rope, orBalancer, be sufficiently strong; there will be no Necessity for the Aironaut to throw out Ballast occasionally; nor for the Observations in the former Part of this Section: theDensitieswill likewise be more easily determined, by theWeights; which shew theEncreaseof Levity and Expansion of the Balloon, at each of thegivenHeights: Allowance being made for the Weight of theBalance Rope,raisedby the Balloon.Method of ascending to a fixedbarometricHeight: there to remain suspendedin Equilibrio.302. The Aironaut, may, at any Height, marked by looking at the Barometer, when at 24 Inches for Example, or as soon as he finds his Balloon sufficiently expanded, pull up the Rope over a Pulley; or, wind it upon a Reel of twoFeet Diameter, within the Car; and continue to do so; till he finds that the Barometer begins torise, (which is a Sign that the Balloondescends), by the additionalWeightof the Balancer just brought into the Car: on which, by preconcerted Agreement, he may throw out awhiteFlag, prepared to hang a Yard below the Car.On Sight of the Flag, the Person at the Reelbelowis to cut the Rope: which Rope, or a Part of it, is to be drawn into the Car.The Balloon will rise no higher; but remain inEquilibrioin the Air, at that Height.
CHAPTERLVI.
Section 299.PREVIOUS to the Ascent, provide a Cord, which shall have sufficient Strength to support twice its own Weight, when so great a Quantity of it iscoiledtogether, as, if extended, woud measure half a Mile or a Mile.
Weigh the wholeCoil, or any Number of Yards, so as to obtain the whole Weight.
Mark the whole Length of the Cord, with differentcolouredWorsted, or otherways, at the Distance of every eight Yards: as asoundingLine.
Note the Marks in a Pocket-Book.
These Things being done; give the Balloon, byinflation, a Power of Levityat leastequal to the known Weight of the Cord: which may be easily obtained by throwing into the Car, alreadyballastedand prepared, a Weight equal tothe Aironaut, together with that of theCord.
The Cord must also, previous to the Ascent, be rolled upon a Reel, (made fast in the Ground) whose Diameter shoud betwoFeet: each Turn of the Wheel may be called two Yards.
A Barometer with an attached Thermometer fixed in the same Frame, also a second or detached Thermometer placed at the Distance of a Yard from the Frame, shoud remain upon the Ground during the Inflation.
The same Apparatus of Barometer with attached and detached Thermometer, shoud be suspended in the Car.
The Instant the Balloon ascends, an Observer below is to note in a Book thePointat which the Quicksilver stands in each of thethreeTubes of the lower Apparatus, also the Time of Ascent: the Aironaut the same.
The Rope is, previous to the Ascent, to be tyed to a Center above the Car: and as soon as the Balloon has elevated the Car 100 Yards; the Observations, as before, are to be set down below, and by the Aironaut: and repeated at the Height of each 100 Yards: a Drum to beat; during the Time each Observationbelowisnotingdown; and the Balloon not suffered to rise, till the Drum has ceased. By such repeatedNotice, andSilence; the Aironaut will know theexact Height, at which the Balloon is checked in its Elevation: and theexact Timeduring which its Elevation is impeded.
This Process is to continue, till the Rope is raised to its full Length.
At which Instant a double-barrel Gun is tobe fired: the exact Time notedbelow: and the Time of hearing the Sound noted above.
These Notes are to be compared at the Aironaut’s arrival on Earth.
300. For suchniceExperiments the Aironaut shoud ascend half an Hour beforesunrise, orSunset: and the Day chosen by the foregoing Rules.
The Air must bequite calm: but it is not necessary that it shoud be free from Clouds or Mist.
When the Rope is at its full Extent, the Operatorbelowis to shorten it, by winding down the Balloon, 100 Yards: the Signalsbelow, being repeated, till the Balloon is arrived within 100 Yards of the Ground.
To estimate the Densities at different Heights.
301. While one Observerbelowis writing down the Observation to be made the Instant the Balloon has risen exactly 100 Yards; another Operator is to weigh, by Hand, with Spring Steel-Yards, the Force of Levity already acquired, which is to be noted down by a third Bystander.
This Process is to be repeated at every 100 Yards.
The Levity, it is true, will encrease as the Balloon rises, (probably in a geometric Progression;)â [100]yet the Cord, by rising with the Balloon, will greatly check it: if, however, it proveinsufficient for that Purpose, and, lest the Cord shoud be in Danger of breaking; the Bottom of the Balloon must be opened, or the upper Valve drawn.
If theCord,Rope, orBalancer, be sufficiently strong; there will be no Necessity for the Aironaut to throw out Ballast occasionally; nor for the Observations in the former Part of this Section: theDensitieswill likewise be more easily determined, by theWeights; which shew theEncreaseof Levity and Expansion of the Balloon, at each of thegivenHeights: Allowance being made for the Weight of theBalance Rope,raisedby the Balloon.
Method of ascending to a fixedbarometricHeight: there to remain suspendedin Equilibrio.
302. The Aironaut, may, at any Height, marked by looking at the Barometer, when at 24 Inches for Example, or as soon as he finds his Balloon sufficiently expanded, pull up the Rope over a Pulley; or, wind it upon a Reel of twoFeet Diameter, within the Car; and continue to do so; till he finds that the Barometer begins torise, (which is a Sign that the Balloondescends), by the additionalWeightof the Balancer just brought into the Car: on which, by preconcerted Agreement, he may throw out awhiteFlag, prepared to hang a Yard below the Car.
On Sight of the Flag, the Person at the Reelbelowis to cut the Rope: which Rope, or a Part of it, is to be drawn into the Car.
The Balloon will rise no higher; but remain inEquilibrioin the Air, at that Height.