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TREATISE
ON
PNEUMATICS:
BEING
THE PHYSICS OF GASES,
INCLUDING VAPORS.
CONTAINING
A FULL DESCRIPTION OF THE DIFFERENT AIR PTTMPS, AND THE EXPERIMENTS WHICH MAY BE
PERFORMED WITH THEM ; ALSO THE DIFFERENT BAROMETERS, PRESSURE GAUGES,
HYGROMETERS, AND OTHER METEOROLOGICAL INSTRUMENTS,
EXPLAINING THE PRINCIPLES ON WHICH THEY ACT, AND
THE MODES OF USING THEM.
Illustrated fij Nunurous jFiite SEooir 3%nzxzbin%8.
BY
MARTIN" H. BOYE, M.D.A.M.
PROFESSOR OF NATURAL PHILOSOPHY AND CHEMISTRY IN THE CENTRAL HIGH SCHOOL OF PHILADELPHIA,
FORMERLY ASSISTANT GEOLOGIST AND CHEMIST TO THE GEOLOGICAL SURVEY OF TH 3 STATE OF
PENNSYLVANIA, MEMBER OF THE AMERICAN PHILOSOPHICAL SOCIETY, ETC. ETC.
PHILADELPHIA:
E. C. & J. BLDDLE, No. 8 MINOR STREET,
(Between Marlcet and Chestnut, and Fifth and Sixth Sts.)
1855.
i. ( ^ Al .
Entered according to the Act of Congress, in the year 1855, by
M. H. BOYE,
in the Clerk's Office of the District Court of the United States for the Eastern
District of Pennsylvania.
STEREOTYPED BY L. JOHNSON & CO.
PHILADELPHIA.
Printed by T. K. & P. G Collins.
Q'OICI
PREFACE.
THE frequent inquiries made in regard to the principles, differ-
ent constructions, and modes of using the different meteorological
instruments, which come within the subject treated of in this
little volume, and the general and increasing interest felt in these
matters, induce the author to believe that the present work will
supply a want which has been much felt. While he has adhered
to a strict systematic arrangement, and, on the part of science,
sacrificed nothing to popularity, he hopes that he has made the
explanations so clear and full as to be intelligible to all. Nor
has he spared any trouble or expense in illustrating the subject by
numerous appropriate wood-cuts made expressly for this work, and
many of them entirely original. For the use of the different instru-
ments a series of Tables has been added, including those of the
Tensions of Vapor of Water, used with the Boiling-Point Barome-
ter and the different Hygrometers, which Tables have been calcu-
lated for this work from those of Regnault, and are here given,
for the first time, complete in English measures and Fahrenheit
degrees.
PHILADELPHIA, May IQlh, 1855.
CONTENTS.
ON INANIMATE MATTER.
GENERAL INTRODUCTION.
Paragr. Page
1. Matter. Sciences. Physical Sciences. 9
2. Forces. Laws. Object of Physical
Sciences 9
3. Life. Physics of Animate Matter
or Physiology 9
4. Physics of Inanimate Matter, how di-
vided 9
5. Descriptive Sciences 10
6. Applied or Practical Sciences 10
7. Mixed Sciences 10
DIVISION I.
PHYSICS PROPER, OR NATURAL PHILOSOPHY.
INTRODUCTION.
8. Physics proper defined 11
9. Plan of distribution of Matter through
Space 11
10. Ultimate construction of matter.
Atoms 11
11. Cohesion 12
12. Different Forms or States of Matter.
Solid, liquid and gaseous states 12
14. Ether, or Imponderable Matter 13
15. Adhesion 13
16. Gravity 13
17. Impenetrability 14
18. Impact or Impulse 14
19. Inertia 14
20. Limit. Form. Numbers 14
21. Motion and Best 15
22. Their relation to matter 15
23. Physics proper, how divided 15
General Table of Divisions and Sub-
divisions of Physical Sciences 16
PART I,
PHYSICS OF PONDERABLE MATTER.
SECTION I.
PNEUMATICS, OR PHYSICS OP GASES.
Properties depending on Cohesion.
24. Expansibility 17
Paragr. Page
25. The Atmosphere 17
26. Different gases of the Atmosphere... 18
27. Extent of Atmosphere 18
28. Exhausting Air-pumps. Single-bar-
relled stopcock -pump 18
29. Mode of Action. Injurious Space... 20
30. Single-barrelled Valve-pump or Sy-
ringe 21
31. Wide-mouthed Receivers and Plate... 21
32. Double-barrelled Exhausting Air-
pump 21
33. Single-barrelled, double-acting 22
34. Improved single-barrelled, single-
acting 24
35. Mode of calculating rarefaction 26
37. Suction by the mouth 27
38. Other means of exhaustion. Filling
of Thermometer-bulbs 27
39. Compressibility and Elasticity of
Gases 27
40. Forcing or Condensing Air-pumps.... 28
41. Single-barrelled 28
42. Receivers and Plate 29
43. Single-barrelled, double-acting 30
44. Mariotte's Law 30
45. Permanent and Liquefiable gases.
Vapors 3,0
48. Diving Bell -31
49. Air-gun 31
50. Other means of compressing gases.
Steam-boiler. Fire-arms 32
Properties depending on Adhesion.
52. Diffusibility of Gases 32
53. Diffusion through Porous Bodies 33
54. Condensation of Gases on Solids.
Hygroscopic Water. Platinum Ig-
niter 33
55. Solution of Gases in Liquids 34
56. Diffusion of Gases in Solution. Re-
spiration. Confining Gases by Wa-
ter and by Mercury 35
Properties depending on Gravity.
57. Weight of Gases 35
58. Specific Gravity of Gases 36
CONTENTS.
Paragr. Page
59. Pressure caused by Weight of Atmo-
sphere 37
60. Torricellian Tube 38
61. Pressure of Atmosphere, how esti-
mated. Used as Unit 38
62. Torricellian Vacuum 39
The Barometer.
63. Cup and Syphon Barometers 40
64. Source of Inaccuracy, how remedied. 41
66. Water Barometer 42
68. Diagonal or Inclined Plane Baro-
meter 43
69. Wheel Barometer 43
70. Huygen's Double-Barometer 44
71. Means of increasing Accuracy in
measuring 44
72. Vernier, its Nature and Construction 44
75. Effects of Capillarity on Barometer.. 47
Table of Correction for same 47
76. Friction and Adhesion of Mercury... 48
77. Expansion by Heat of Mercury, and
of Scale 48
78. Marine Barometer 50
79. Gay-Lussac's Portable Syphon Baro-
meter 51
80. Preventing Air getting into the Va-
cuum 53
81. Accurate Levelling Barometer 53
82. Standard Barometers 55
83. Self-registering 55
84. Objections to Mercurial Barometer.. 55
85. Substitutes for Mercurial Barometer. 56
86. Sympiesometer 56
87. Boiling-Point Barometer 57
88. Aneroid Barometer 58
89. Metallic Barometer (Bourdon's) 61
90. Nature of Barometer 62
91. Manometer 62
Uses of the Barometer.
92. As Weather-glass 63
93. Range and Variations of Barometer. 65
94. For measuring Heights. Principle of. 65
Mode of Calculating 67
96. Example 69
98. Rapid Decrease in Pressure and
Density of the Atmosphere 70
99. Mode of taking Observations for
Levelling 70
100. Estimating the true Volume of
Gases, and from it, their Weight.. 71
Mariotte's Law.
101.. Experiments to prove Mariotte's
Law 73
103. Mariotte's Tube 75
104. Exceptions to Mariotte's Law 75
Pressure-gauges.
105. Mercurial Exhaustion-gauge for Air-
pumps 75
Paragr. Page
106. Mercurial Pressure-gauges 76
107. Condensed-Air Pressure-gauges 77
108. For very high Pressures 78
109. Of very small Dimensions 79
110. Steam-gauges (Manometers). Safe-
ty-valves 79
Ezperiments to illustrate Pressure of
Atmosphere.
111. Fountain in Vacuo 80
112. Mercurial Rain 80
113. Bursting of Bladder '80
114. Upward Pressure of Atmosphere.... 80
115. Magdeburg Hemispheres 81
116. Pressure on Human Body 81
Experiments to illustrate Expansibility, Elas-
ticity, and Compressibility of Atmospheric
Air.
117. Difference between Expansibility
and Elasticity. Tension 82
118. Inflation of Bladder by Expansi-
bility 83
119. Mechanism of Respiration 83
120. Expulsion of Air from Water by
Exhaustion 84
121. From the Pores of Charcoal. Their
filling with water Si
122. Hero's Ball 84
123. Condensed- Air Chamber of Hydrau-
lic Engines 85
Impact and Inertia of Gases.
124. Resistance of Air. Windmill Ex-
periment 85
125. In a Vacuum all Bodies fall equally
fast. Feather and Guinea Ex-
periment , 86
126. Resistance of Air to Projectiles.
Flight of Birds 87
127. Winds. Table of their Velocities
and Force 87
128. Anemometer 88
129. Efflux of Gases into a Vacuum
through Capillary Orifices (Effu-
sion) 88
130. Through Capillary Tubes (Transpi-
ration) 89
131. Efflux of Gases into the Atmosphere. 89
132. Revolving Gas Jet 89
133. Pneumatic Paradox 90
VAPORS.
134. Circumstances under which formed. 91
135. Nature of Vapors 91
Formation of Vapors in a Va
136. Has a Limit. Maximum Quantity
and Tension; depends on Tem-
perature 92
CONTENTS.
vii
Paragr. Page.
137. Quantity of Vapor estimated from its
Tension 93
138. Table of Maximum Quantities and
Tensions 93
139. Tension or Elasticity of Steam at
high Temperatures 93
140. Expansion of Vapors by Heat 94
141. Vapors not filling space to Satura-
tion may be subjected to Pressure
and Cold 95
142. Illustration as regards Pressure 95
143. As regards Cold. Dew-point. Proof
of Saturation 96
144. Boiling in a Vacuum, how produced. 96
145. Culinary Paradox 97
146. Papin's Digester 97
147. Theoretical Stop to Evaporation... 97
148. Different Volatility of Substances.. 98
149. Modes of increasing Evaporation in
a Vacuum 98
150. Applications in Chemistry 98
Formation of Vapors in a Gas.
151. Has a Limit. Maximum Quantities
and Tensions the same as in a
Vacuum 99
152. Difference between the Formation of
Vapors in a Gas and in a Vacuum 100
153. Boiling in Open Air. Simmering. 100
154. Boiling-Point of different Sub-
stances 101
155. Boiling-Point altered by change in
Pressure 101
156. Limit to Boiling in a Vacuum 101
158. Modes of increasing Evaporation in
a Gas 101
159. Applications in Chemistry 102
Vapor of Water in the Atmosphere.
160. Different States in which Water
exists in the Atmosphere. Dew.
Fogs. Clouds ; different Varie-
ties of. Rain; Rain-gauge or
Ombrometer. Hail. Snow 102
161. How Vapors affect the Atmosphere. 103
162. Moisture or Humidity of the Atmo-
sphere. Relative Moisture or
Humidity 103
163. Amount of Vapor, how estimated
by Chemical Method... 104
Hygrometers.
164. Their use. Mode of finding the
Relative Humidity from the
Dew-point and the Temperature
of the Atmosphere 105
165. To find Tension of Vapor and Dew-
point from Relative Humidity
and Temperature of Atmosphere 106
166. To find per centage of Vapor by
Volume .. 106
Paragr. Page.
167. Per centage of Vapor by Weight... 106
168. Absolute Weight of Vapor in a cer-
tain Volume 107
Hygrometers giving the Dew-point.
169. Darnell's Hygrometer 108
170. Bache's Hygrometer 109
171. Regnault's Hygrometer 109
172. August's Psychrometer, or the Wet-
Bulb Hygrometer 110
173. Formula for Tension of Vapor, and
Dew-point, from Wet-Bulb Hy-
grometer Ill
174. Example 112
175. Precautions in using Wet-Bulb
Hygrometer 113
Hygrometers acting by Absorption.
177. Their mode of Action 113
178. Saussure's Hair Hygrometer 114
179. Table of Relative Humidities cor-
responding to its Degrees 115
180. Objections to the Hair Hygrometer 115
181. Hygroscopes made from Whale-
bone, Wood, Twisted Strings,
Beard of Sensitive Oats, Blad-
der, &c 115
Tables.
TABLE I. Correction for Temp, for Barome-
ters mounted in Wood.
TABLE II. Correction for Temp, for Baro-
meters with Brass Scale, extending the
whole length.
TABLE III. For finding differences in Height
between two Places from Barometric Ob-
servations.
TABLE IV. Correction of same for Latitude.
TABLE V. Correction of same for Altitude.
TABLE VI. Conversion of French into Eng-
lish, and of English into French mea-
sures, &c.
TABLE VII. Maximum Tension, or Elastic
Force of Vapor of Water for every 0.2 de-
gree from 214 to 185. For Boiling-Point
Barometer.
TABLE VIII. Maximum Tension of Vapor
of Water for every degree from 185 to
104.
TABLE IX. Maximum Tension, or Elastic
Force of Vapor of Water, for every 0.2
degree from 204 to 0, and for every de-
gree from to 31. For (Dew-Point)
Hygrometers.
ON
INANIMATE MATTER
GENERAL INTRODUCTION.
1. BY Matter we understand all that acts on our senses. Matter, there-
fore, constitutes the whole external or Material World, the Universe.
Our knowledge of matter systematically arranged constitutes the Sciences
of Matter, or the different Material or Natural or Physical Sciences, or
Physics in its widest sense ; in contradistinction to the sciences of the
mind, or the Mental and Moral Sciences, treating of the internal or
immaterial world.
2. The different phenomena and properties of matter we account for
by ascribing them to certain causes inherent in matter itself, which we
call Forces. These forces are always found to act according to certain
rules or laws. The main object of the physical sciences must, therefore,
be to discover these forces, and expose the laws according to which they
act.
3. But besides the general forces, which all matter obeys at all times,
matter is also capable of being brought under a peculiar influence, which
we call Life. While under such influence it is called Animate matter, in
contradistinction to which, when not under this influence, it is called
Inanimate matter. We therefore get two main branches of the physical
sciences: Physics of Animate matter, or Physiology (Special Physics),
which treats of Life and the manner in which matter is influenced by it,
or of Animate matter; and Physics of Inanimate matter (General Physics),
which treats of Inanimate matter.
4. Our knowledge of inanimate matter must refer either to its place, or
to its nature; we therefore get two divisions of Physics of Inanimate
10 BOYE'S INANIMATE MATTER.
matter, Physics proper, or Natural Philosophy, which treats of the place
of inanimate matter, and Chemistry, which treats of its nature.
5. The physical sciences have each their descriptive part, describing
the different objects or bodies formed in nature by the forces or influences
of which they treat. These descriptive parts are often considered as sepa-
rate sciences, and called the sciences of Objects, in contradistinction to
which the others, of which they are only descriptive parts, are called the
sciences of Phenomena. Thus the descriptive part of Physiology, or a
description of all the different forms of matter assumed under the influ-
ence of life, or animate objects, constitutes Natural History, of which
again Anatomy is a subordinate branch. Uranography is a descriptive
part of Physics, Mineralogy of Chemistry, and Geology, Meteorology
and Physical Geography, are descriptive parts of Physics and Chemistry.
6. The above main branches and divisions of the natural sciences, when
applied to particular purposes, as the performance of certain mechanical
operations, or the production of certain chemical compounds, required for
our necessities or comforts or other relations of social life, constitute the
different applied, or practical, or industrial sciences. These are used in
the different trades, manufactures and arts, and a systematic arrangement
of the greater number of them is often called Technology. Agriculture,
Surgery, Medicine, &c., are instances of applied branches of Physiology,
in connection with Physics and Chemistry.
7. The different economical, political and philological sciences are
combinations of mental and physical sciences, pure or applied.
10
DIVISION I.
PHYSICS PROPER, OR NATURAL PHILO SOPHY.
INTRODUCTION.
IYSICS proper, it lias been said in a general way, treats of the place
of matter. But as we ^ount for all phenomena connected with matter
by ascribing them to certain causes inherent in matter, which we call
forces, which forces always act according to certain rules or laws. Physics
proper must treat of the forces, by which matter holds its place in space,
and expose the laws according to which they act.
9. That which first strikes us in regard to the place of matter on a
large scale, is, that we do not find it to be equally distributed through
space, but collected in large masses, constituting the heavenly bodies and
the earth, and the space between them to be comparatively void.
10. "We have reason to believe, that internally matter is constructed on
a similar plan, so that any portion of it does not consist of matter uni-
formly diffused through the space which it occupies, but that the matter
of which it consists is collected in small particles called atoms, with a
small space between them, which is comparatively void. These ultimate
particles or molecules are called atoms (from a privative and re//vd>
(temrio) I cut), meaning what can not be cut or divided, because they
are considered to be indivisible and indestructible. Though practically
they may be considered infinitely small, still in reality they have a
certain definite size and form. Their form is generally considered to be
that of small solid spheres or spheroids, inside perfectly uniform; single
spheres for simple bodies and clusters of such spheres for compound
bodies.*
* The main arguments in favor of the existence of atoms with spaces between them
are; the general nature of chemical combination with the laws of definite and multiple
proportions, isomerism and allotropism, for which see under Chemistry; cleavage and
crystallization, see under Stereotics; expansibility of gases, see Pneumatics; the
11
12 BOYE'S INANIMATE MATTER.
11. All bodies, by which we understand limited portions of matter, must
therefore consist of aggregations of such atoms. These atoms being not
in contact are kept at certain extremely small but definite distances from
each other by two forces, an attractive force, which tends to approach
them to each other, and a repulsive force, which tends to separate them.
The resulting effect of these two forces is called COHESION, and constitutes
the force with which each atom is held in the same relative position to
the other atoms of the same kind of matter. Compressibility and Elas-
ticity are properties of matter depending on this same force.
. According to the greater or less strength of the above attractive and
repulsive forces between the atoms, constituting the degree of cohesion,
matter presents itself in one or the other of the following three states or
forms.
1st. The solid state. Whenever the attractive and repulsive forces
between the atoms are great, the atoms are kept firmly in their relative
position, so that they offer considerable resistance to any force that tends
to move them among themselves, or to separateihem from each other.
In this case, therefore, the cohesion is said to be great, and the matter
presents itself in the solid state.
2d. The liquid state. In this state matter presents itself when the
attractive and repulsive forces between the atoms are but small. The
atoms are then held in their relative position with but a slight force, so
that they can easily be moved among themselves, or separated from each
other. In liquids, therefore, the cohesion is small.
3d. The gaseous state. This state matter assumes when the atomic
repulsive force is greater than the attractive. The atoms then have a
tendency to separate from each other and spread themselves through
space, unless prevented by some other cause. This property in gases is
called Expansibility, and distinguishes them from liquids. Cohesion in
this case is said to be negative. They also offer little or no resistance to
the motion of their particles among themselves, in which point they re-
semble liquids. For this reason liquids and gases are comprised together
under the common name of fluids in contradistinction to solids.
13. One and the same kind of matter may often, under different circum-
stances, exist in either of the above three states. Thus water when ex-
posed to cold becomes solid or ice, and by heat may be converted into gas
or steam. But matter can only exist in one state at the same time, and
under the same circumstances it nearly always assumes the same state.
expansion of all matter by heat, see Thermics ; and the undulatory nature of light, and
its passage through all forms of ponderable matter, see Photics. For the particulars
regarding the form, size and weight of atoms, see under Stereotics.
12
PHYSICS PROPER, OR NATURAL PHILOSOPHY. 13
14. The ethereal state. The existemce of a fourth state of matter is ren-
dered highly probable, filling the spaces between the atoms of the above
three states (the interatomic spaces), and the spaces between the planets
and between the stars (the interplanetary and interstellar spaces). This
state is called the Ethereal, and the matter itself Ether.* That Ether
must differ materially from other states of matter, follows from the fact,
that it fills the spaces between their atoms. Either therefore it can ,not
be composed of similar ultimate atoms, or these atoms must at least be of
a much smaller size. As it has been found to offer a sensible resistance
to the comets in their motion, it must, as it will afterwards be understood,
possess inertia and in this point resemble the other kinds of matter. If,
however, it is affected by gravity so as to possess weight, (see further on),
this is so inconsiderable, that it cannot be ascertained by the same means
by which it is proved for other matter, hence it is generally called Im-
ponderable matter, in contradistinction to which the other states of matter
are called Ponderable matter. It has not been ascertained whether other
states of matter may also exist in the Ethereal state, or the Ether itself
be condensed or converted into the others. On the whole, though its
existence is well established, our knowledge of its nature is yet but very
imperfect.
15. The same attractive and repulsive forces, which exist between the
atoms of matter of the same kind, we also find between the atoms of
different kinds of matter, by which these are held in their relative posi-
tion at a small distance from each other. The resulting effect is in this
case called ADHESION, because if after having brought the atoms of two
different bodies together, we again attempt to separate them, particles of
the one often remain by this force attached, or adhere to the other. Thus
if we dip a glass rod into water and then again withdraw it, some of the
water will adhere to the glass in preference to cohering to the other par-
ticles of itself. Capillary attraction and solution are caused by the same
force.
16. The attractions and repulsions, of which we have spoken (Cohesion
- and Adhesion), do not extend perceptibly beyond a very small distance,
probably not beyond the distance of proximate or neighboring atoms.
We observe, however, another attractive force to exist between atoms of
the same or different kinds of matter, and acting also at distances greater
than the distances of proximate atoms, only in a certain diminishing ratio.
* The main argument for the existence of Ether in all these spaces and others, not
filled with ponderable matter, we have in the passage through them of light, which can be
proved to be formed by undulations, which therefore require the existence of an undula-
ting medium.
14 BOYE'S INANIMATE MATTER.
As it thus acts on all the atoms, of which a body consists, and at great
distances, it becomes also an attraction between masses of atoms, or bodies
towards each other. This attraction is called GRAVITY, and must there-
fore be greater according to the number of atoms in the different bodies.
We thus find that a very strong attraction exists by gravity between the
heavenly bodies and the earth, and between the earth and all terrestrial
bodies on or near its surface; but it is exceedingly small between the
terrestrial bodies themselves, though it can be proved also to exist be-
tween them according to their size. Gravity has by some been con-
sidered as the result of the attractions of cohesion and adhesion, but
this is Hot probable; at all events we are not acquainted with a corres-
ponding repulsive force acting at a distance like Gravity.
17. It has been stated that the ultimate atoms are considered solid.
They therefore allow no other atoms of the same, or any other kind of
matter to enter or occupy the same space at the same time. This property
of matter is called IMPENETRABILITY. The space between the atoms may
be diminished (Compressibility), but the atoms of the same body can
never be forced into each other even by the greatest pressure, nor will
they allow the atoms of any other body to be forced into their place.
One kind of matter may, however, allow the atoms of another kind to
penetrate with considerable facility into the spaces between its atoms,
while it will resist with great force the further approach of its own
atoms. This property is called Diffusibility, and depends on the attrac-
tion, which has been spoken of before as Adhesion, and is particularly ob-
served between the atoms of solids and liquids, and also between the atoms
of different kinds of gases.
18. When matter has been influenced by a force to move, and in its way
meets other matter, so that it can not continue its motion without putting
this matter also in motion, we find this latter to take place, and a portion
of its own motion to be transferred to it. We thus find, that motion is
transferable by IMPACT or IMPULSE from one portion of matter to another.
19. Matter has also an inherent force to preserve its state of rest or
motion. This force or property of matter is called INERTIA, and is gene-
rally expressed thus, that matter when at rest cannot by itself begin
motion, nor when in motion can it alter this so as to pass to rest, or to a
slower or faster motion, or in a different direction, unless influenced by
some other cause.
/ f\ 20. With the idea of matter and its existence is necessarily given the
\ idea of space to exist in. Where one kind of matter ceases and another
begins, there must be a limit, and all limited portions of matter, or bodies,
must therefore have a Form. But the abstraction of space and
14
"R.
PHYSICS PROPER, OR NATURAL PHILOSOPHY. 15
matter, and its separate consideration can only be made in the mind, and
constitutes, therefore, a purely mental science, Geometry, which does not
belong to the natural sciences, while the application of its results to the
forms of matter, as they actually occur in nature, is of the utmost import-
ance to them (Crystallography, &c.). The same is the case with the
abstraction of the idea of repetition of separate but like portions of matter
or Numbers, and their separate study, which constitutes Algebra, and in
its application is of equal importance to the natural sciences.
1. Matter, while it by its own inherent forces influences other matter
and itself to motion, is equally susceptible to the forces of all other matter,
and will move under their influence. The influence of a single force is to
move it in a straight line. But as it is always acted on at the same time
by a number of forces, and has to move according to all of them, its
motion is always more or less complex. If at the same time matter be
influenced by different forces to move equally in opposite directions, it will
retain the same place or be at rest. Though experience teaches us that
all matter is in constant motion, no particle retaining the same place for
any length of time, so that there is no absolute rest, still a body may be
influenced so as not to alter its position in regard to surrounding objects,
and we then generally say, that it is at rest, though it is only relative or
apparent rest.
22. As the amount of matter in existence always remains the same, and
matter, therefore, cannot be destroyed any more than created, the amount
of its inherent force to produce motion, and the effects produced by it at
any moment must also remain the same. Applying this to the forces
producing motion, it follows from this and what has been said of Inertia,
that motion can no more be destroyed or created than matter itself; and as
all matter is now in constant motion, motion must be coeval with matter.
23. The forces and properties of which we have spoken so far (Cohesion,
Adhesion, Gravity, Impenetrability, Impact and Inertia), are the main
causes due to ponderable matter itself, on which depends its position in
space. There are yet other attractions and repulsions between the atoms
and masses of ponderable matter, such as the expansion by heat, the
attractions and repulsions by electricity, &c. ; but these seem to be con-
nected with or imparted to it, by certain states or motions of the ether
between its atoms, and the causes of which are designated as light, heat,
magnetism and electricity. They will, therefore, be treated of separately
in connection with the ether. We thus obtain two parts of Physics
proper, Physics of Ponderable matter, or Mechanical Physics ; and Physics
of Imponderable matter, or Ethereal Physics, which treats of the ether, and
the influences it exercises on ponderable matter. Physics of Ponderable
15
16
BOYE'S INANIMATE MATTER.
matter we again subdivide iiito three sections; Physics of Solids, or
Steoretics; of Liquids, or Hydraulics; and of Gases, or Pneumatics.
Physics of Imponderable matter is sub-divided into four sections; Physics
of Light, or Photics, or Optics; Physics of Heat, or Thermics; Physics
of Magnetism, or Magnetics; Physics of Electricity, or Electrics. The
following table will exhibit the respective divisions and subdivisions of the
Natural Sciences.
' Physics of
Solids, or
Stereotics.
Physics of
Ponderable
Physics of
Matter.
Liquids, or
(Mechanical
Hydraulics.
Physics.)
Physics of
Gases, or
Pneumatics. "
f Physics
proper, or
Natural
Philosophy.
r Physics of
Light, or
Photics, or
Optics.
Physics of
Inanimate
Matter.
Physics of
Imponderable
Matter.
Physics of
Heat, or
Thermics.
(General
Physics.)
(Ethereal or
Imponderable
Physics.)
Physics of
Magnetism, or
Magnetics.
Physics of
PHYSICAL OB
NATURAL
SCIENCES.
(Physics in its
Chemistry.
(Atomic or
Chemical
Physics.)
Electricity, or
Electrics.
widest sense.)
Physics of
Animate
Matter, or %
Physiology.
(Special
L Physics.)
3>
16
PART I.
PHYSICS OF PONDERABLE MATTER.
THOUGH in a systematic point of view it would be better to treat first
of solids, still as it practically is more important, first to have a know-
ledge of the physical properties of gases, we shall begin with these.
SECTION I.
PNEUMATICS, OR PHYSICS OF GASES.
The word Pneumatics is derived from a Greek word -KVWIIO. (pneuma),
signifying air.
Properties of gases depending on Cohesion.
24. We have seen that whenever the repulsive force between the atoms
preponderates over the attractive, matter assumes the state called the
gaseous or aeriform. Gases, therefore, not only possess fluidity like liquids,
that is, they offer but a slight resistance to the moving of their particles
among themselves, but their atoms have also a constant tendency to recede
from each other, and therefore to extend themselves over space, until limited
or confined by some outer boundary, or restrained by some counteracting
force. This property is called Expansibility, and constitutes the main
difference between gases and other states of matter.
25. Nature has placed us in an ocean of gases called the Atmosphere,
which forms the uppermost portion of the whole earth. Thus circum-
stanced, we are apt to feel less conscious of their material existence and to
overlook the fact, that they form the medium, through which we generally
receive the impressions on our senses from other bodies. Thus when we
hear a sound caused by the vibrations of a solid, it is not these latter that
act on our ears, but the vibrations of the air produced by them. And if,
in the same manner, on account of the extreme fluidity and tenuity of the
B 17
18 BOYE'S INANIMATE MATTER.
atmospheric gases, they under ordinary circumstances are not perceived,
we may easily render air as tangible as a solid or liquid by allowing it to
impinge against any part of our body; for instance, by blowing on it.
And even to our eye-sight air is as visible as any other kind of transparent
matter; we have colored gases, and a bubble of a colorless gas is as
visible in water, as a drop of water is in air. Their effect on the senses of
smell and taste is also familiar. It will also be shown, hereafter, that we
are capable of weighing gases like any other forms of ponderable matter.
26. Atmospheric air is, however, not one kind of gas, but a mechanical
mixture of four different gases. Oxygen, about -J by vol., and Nitrogen, about
-J, or more accurately, in the relative proportion to each other of 20.8 ox.,
to 79.2 nitr., form the main portions of it. Besides these it contains small
but varying quantities of Carbonic acid (about J per mille), and Yapor of
water ( to 2 per cent.).
27. On account of its expansibility it might be supposed, that the at-
mosphere surrounding the earth would extend itself infinitely far into
space. This is, however, not the case. We can prove from the property
of refraction, which the atmosphere possesses, or that of bending the light from
its straight path, when penetrating in an oblique direction through its
strata of different densities, that it does not extend sensibly beyond the
height of 45 miles. It is therefore probable, that as the rarefaction of the
atmospheric gases increases with the distance from the earth, their expan-
sibility also becomes less, and is at last overcome by gravity, drawing
them toward the earth, so that where these two forces are equal, they
will assume a definite limit. This is confirmed by the experiments of
Faraday, according to which the vapors of mercury enclosed in a tall jar,
only rise to a certain height, presenting an upper level surface. If this
be correct, the different gases of which the atmosphere is formed, ought to
assume each a separate level at different heights from the surface of the
earth, according to their different densities. This might, however, be pre-
vented by the commotion caused by currents.
28. The expansibility of gases affords us the means of removing them
from any containing vessel, or of rarefying them to any extent. Appa-
ratus constructed for this purpose are called exhausting air-pumps. In
the simplest form an exhausting air-pump consists of a single hollow
cylinder, generally of brass (see a Jigs. 1 and 2), called the barrel, and
having the inside ground perfectly true, so that a short solid cylinder b,
called the piston, may be moved in it perfectly air-tight by the aid of the
piston-rod c, furnished for this purpose with a handle d. At the
bottom of the barrel is an orifice, which forms the beginning of a passage,
1 and efig. 2), which at its other extremity is furnished with a
18
PNEUMATICS.
Fig. 1.
19
Fig. 2.
Fig. 3.
screw /, by which it can be attached to any vessel or receiver h, from
which it may be desirable to exhaust the air. Across this passage ef,
as near as possible to the barrel, is inserted a conical piece
of metal g figs. 1 and 2, and represented separately by
fig. 3, called the plug, fitting across the passage in a
corresponding conical hollow, so as to be movable round its
axis, which is at right angles to the passage; the whole,
the passage with its conical hollow and the plug, con-
stituting a stop-cock. The plug of a stop-cock has always
one perforation through it, which in one position forms a
continuation of the passage; but when the plug is turned 90 degrees
round its axis, so as to have the perforation at right angles to the passage,
this is interrupted. The stop-cock used in this case is what is termed
a two-ways stop-cock, having two perforations, see fig. 3, the usual one
* to close and interrupt the passage e f between the barrel and the
receiver h, to which the air-pump is attached, see fig. 1, and a second
one k fig. 3, which when the first perforation is at right angles to
the passage, see fig. 2, forms at first a continuation of it, but then turns
so as to run parallel with the axis of the plug, and terminates outward
into the atmosphere, thus establishing a communication between the barrel
and the outer air, when the communication with the receiver is shut off,
as seen in fig. 2, which, however, is interrupted when the communication
with the receiver is open, as seen in fig. 1.
29. If now after having attached the air-pump to any vessel or receiver
h, from which we intend to exhaust the air, and having turned the
19
20 BOYE'S INANIMATE MATTER.
stop-cock g, so as to establish a communication between it and the barrel,
see fig. 1, we draw out the piston as represented in fig. 2, the air
in the receiver will expand and fill both the receiver and the barrel. The
stop-cock is then turned so as to shut off the communication between the
receiver and the barrel, and to open it between the barrel and the outer
atmosphere, as represented in fig. 2, and the piston pushed in to the
bottom of the barrel, by which the air in the barrel is expelled into the
atmosphere. If then again by turning the stop-cock, the communication
be interrupted between the barrel and the atmosphere, and opened between
the barrel and the receiver, and the piston drawn out, and the same process
repeated, a portion of air will by every outward stroke of the piston enter
from the receiver into the barrel, and by the next inward stroke be ex-
pelled into the atmosphere. This might thus be continued as long as the
remaining air retains its expansibility, though a last portion, however
small, would always remain behind. Practically, however, it is not pos-
sible to carry the exhaustion this far j for, however near the plug of the
stop-cock be placed to the barrel, a small space will always remain between
it and the bottom of the latter, called the Injurious Space, into which the
piston cannot enter. After the piston has been pushed to the bottom to
expel the air in the barrel into the atmosphere, this space will always re-
main filled with air of the same density as the atmosphere. If this air
which thus remains in the injurious space, by expanding over the barrel
when the piston is again drawn out, be yet of the same density as the
remaining air in the receiver, none of the latter can enter into the barrel,
when the communication between them is established, and thus all further
exhaustion becomes impossible. Besides this, such apparatus are often apt,
from imperfect make, to admit small portions of air by leakage.
30. Stop-cock pumps have the inconvenience, that the stop-cock must
be turned at every stroke. This may be performed by mechanical contri-
vances connecting it with the motion of the piston-rod, and they then con-
Fig. 4.
.
PNEUMATICS. 21
stitute very superior pumps. It is, however, more convenient and less
expensive to substitute pneumatic valves, which are self-acting. Such
valves are generally constructed of a strip of oil-silk, see v and v 1 - fig. 4,
and v fig. 5, fastened by its two extremities, so as to lay close over the
orifice by which the passage terminates, or when the valve
is placed in the passage itself, the latter is made to ter-
minate by an orifice s in a projection, over which the oil-
silk v is tied or otherwise fastened, as shown by fig. 5,
which represents separately the valve-piece screwed into
the piston of fig. 4. Such valves will then allow the
air to pass in the one direction between it and the orifice, but as soon
as the air presses in the opposite direction, the oil-silk is forced close
against the orifice and prevents the air from passing in that direction".
Instead of the two-ways stop-cock, two such valves are substituted, see v
and v*fig. 4. One v is placed in the bottom of the barrel over the orifice
-- of the passage leading to it from the receiver, so as to allow the air to
pass from the receiver into the barrel but not back again. The other
valve v 1 is placed in a passage through the piston, permitting the air to
pass out through the piston from the barrel into the atmosphere, but not
back again. It will thus be evident, that every time the piston is drawn
out, the air in the receiver is allowed to pass through the valve v into the
barrel, the valve v 1 in the piston remaining closed. When, on the con-
trary, the piston is pushed in, the valve v between the barrel and the
receiver closes, and the air in the barrel is expelled through the valve
v 1 in the piston.
31. As it is often desirable to place in the exhausted vessel different
objects or apparatus, it becomes necessary to have pneumatic receivers
with large mouths or openings. They are then generally made bell-shaped
or cylindrical, closed at the top, see hfig. 4, but open at the other ex-
tremity, the edge of which is ground true, so as to fit air-tight on a brass
or glass plate p, also ground perfectly plane, and having an opening in
its centre leading to a passage furnished at its other extremity with a stop-
cock and a screw, to which the air-pump may be attached. Any object
may then be placed on the plate, after which the bell jar, having had its
edges greased, is inverted over it and pressed with the edges against the
plate, so as to form a perfectly air-tight joint.
32. A single barrelled air-pump, or Syringe, as called when small and
worked by hand, always acts unequally, requiring, on account of the
atmospheric pressure on the piston (see further on), much more force to
move the latter out than back again. To avoid this and also to expedite
the exhaustion, which is a tedious process when the capacity of the barrel
21
22
BOYE'S INANIMATE MATTER.
is small in proportion to that of the receiver, double-barrelled air-pumps
are constructed, see fig. 6. These consist of two complete air-pumps,
each barrel a and b having its piston and two valves, one in the piston
Fig. 6.
and the other at the bottom of the barrel in the passage to the receiver.
But these two passages unite into one leading to the receiver 7i, ter-
minating at the plate. The piston-rods are furnished with teeth, so as to
form racks c c, which are moved by a small cog-wheel or pinion c?, to
the axis of which is attached a two armed lever e, with handles f.
By moving the lever and consequently turning the pinion in alternate
directions, one piston is always moved up, while the other is moved down,
thus, while the one barrel is exhausting the receiver, the other is dis-
arging air into the atmosphere.
13. ^foratead of a double-barrelled air-pump, a single-barrelled but double-
"ng may be used, as represented in fig. 7. In this case the cover of the
barrel must be air-tight, and the piston-rod made to slide air-tight through
it by means of a stuffing box or packing screw. This consists of a hollow
cylinder s fig. 7, made in the cover round the piston-rod c, where it
passes through it. Into this stuffing box, the bottom of which has a per-
foration, merely sufficient to let the piston-rod pass through it without
friction, the stuffing or packing is introduced, consisting of oiled hemp or tow,
or circular pieces of leather (washers or collars), with perforations through their
22
PNEUMATICS.
Fig. 7.
23
middle, barely sufficient to allow the piston-rod to be pushed through them.
A screw stopper /, also perforated through its middle, but so as to allow
the rod to pass easily through it, is then screwed down into the stuffing
box, so as to force the hemp or leather washers against the piston-rod, so
that the latter may slide air-tight through it. The barrel has four valves,
u and u v and v which in this case, as always when the pumps are
large and subject to constant wear, are made of metal, and have then
generally a conical shape, fitting air-tight in a corresponding conical
aperture called the valve-seat. By any pressure from the one side, these
valves are forced from their seat, while pressure from the other side will
force them back again. To restrain their motion and secure their easy
return into their seat, they are, in most cases, furnished with a stem,
which slides in a cross-piece or guide. As the air when rarified would soon
become incapable of opening, by its expansibility, such valves, they must,
for exhaustion, as in the present case, be moved by some mechanical con-
trivance. Of the above four valves, two, v and v open inward to admit
the air from the receiver h into the barrel, and are worked by a valve-rod
o sliding air-tight through the piston b. The two others, u and u open
outward to let the air out from the barrel into the atmosphere, and are
held in their places by spiral springs. In order to secure their opening to
expel the air, they have a short stem projecting into the barrel, against
which the piston strikes, when it arrives near either end. Leading from
the valves, v and v which open inward, are two passages, L and t u
23
BOYE'S INANIMATE MATTER.
Fig. 8.
uniting into one t leading into the receiver h through the plate p.
Being made of lead, and therefore flexible, the tube t may easily be con-
nected or disconnected with the plate by a knob and gallows-screw joint m.
It will easily be seen that by each stroke the piston must, on the one side,
draw air in from the receiver, while on its other side it expels the air from
the barrel into the atmosphere. Fig. 8 gives a full view of a pump of
this kind, constructed by Dr. Hare, and used by him for many years in
his Laboratory. It has two additional passages leading from the valves u
and u uniting also into one, open to the atmosphere at n. These, how-
ever, are not necessary when used only for exhaustion.
34. Fig. 9 exhibits another efficient single-barrelled but single-acting
exhausting air-pump, of Boston manufacture, often met with, and known
as an Improved ( Leslie' Air-pump. The piston-rod c passes air-tight
through a stuffing-box s, in the top of the barrel a, its end sliding in a
cross-piece or guide d, to keep it perpendicular during its motion; t t is
PNEUMATICS.
Fig. 9.
25
the tube forming the passage from the barrel to the plate p, into the
receiver h. The pump has two valves, one in the piston, opening from
the receiver towards the top of the barrel, the other in the top of the
barrel at v, opening from this into the atmosphere. These valves are made
of circular pieces of thin calf-skin soaked in oil and lard, laying close over
the orifices, that at v being fastened on one side by the cap-piece screwed
down over it. From this latter valve the tube u, which is removable,
leads into a cistern f, open to the atmosphere and intended as a recep-
tacle for the oil, as also for ether, or other volatile liquids, which often
have to be removed as vapors from the receiver by exhaustion and may
condense in the barrel or the tube, and thus be forced out through it.
25 3
26 BOYE'S INANIMATE MATTER.
"When the piston is pushed in, the valve at v prevents the air from entering
into the barrel, and a vacuum is formed in the barrel above the piston,
into which the air enters, by its expansibility, from the receiver and barrel
below the piston through the valve in the latter; when the piston is raised,
the air above the piston cannot return through the valve in it, and is
forced out through the valve at v in the top of the barrel, while the barrel
below the piston is again filled with air from the receiver, following, by
its expansibility, the piston as it moves out. This portion of air in the
barrel below the piston, will then again pass through the valve in the
piston to above it, when this is again pushed in, and by the next outward
stroke will be forced out as before. This pump has the advantage over
other single-barrelled, single-acting air-pumps, that after the first outward
stroke has been performed, all the subsequent ones are, as in the double-acting,
performed through the greater part of their motion, not against the atmo-
sphere, but against a partial vacuum, until the piston arrives near the top,
when the air becomes condensed to the same density as the outer atmo-
sphere, and of course the last effort to expel it through the valve at v, must
be against the whole atmospheric pressure. To carry the exhaustion to
the furthest possible limit, the tube u, may be removed and a small ex-
hausting syringe screwed on, by which a vacuum may be produced
above the valve at v, by which the injurious space below the same valve
will remain filled with air of much less density than the atmosphere,
and thus have less effect when expanding in the barrel by the inward
stroke of the piston, by which the exhaustion may be carried much
further.
35. The amount of air remaining in the receiver at any moment during
the process of exhaustion, or the degree of rarefaction, may be calculated,
assuming that no leakage takes place, by knowing the relative capacities
of the receiver and the barrel. For calling the former R and the latter B,
and the ordinary density of the air D, we have after the first stroke, that
the air in the receiver fills both the receiver and the barrel, and its density
after the first stroke D t must therefore be to its former density D, inversely
11 T?
as the spaces occupied, or that D t : D : : p : ^; hence D a = D.
Jtv-j .15 xv Jtx | Jt>
After the second stroke we get in the same manner the density
D =
R
,
R+B R-fB R-f B R+B
D == ( -JL-Yl), and at the nth
V/
stroke D n == ( __ ^) D. Thus if the barrel have | the capacity of the
"R
receiver, we have R = 9, B = 1, and -__ , = and the density or
R-f-B 10
26
PNEUMATICS. 27
quantity remaining in the receiver at the 3d stroke, = Cri
of the original density or quantity.
36. The rarefaction at any time is, however, generally estimated by a
barometer guage connected with the receiver, see mfig. 6 and#,/#. 9,
the principle of which will be explained hereafter under pressure-guages.
37. Suction by the mouth depends on the same principle as exhaustion
by an air-pump. The vessel is first connected by the lips with the mouth,
and the air then expelled from the mouth by pressing its walls close to-
gether. A vacuum is then produced in the mouth by withdrawing the
tongue from the roof of the mouth without admitting any air, which con-
stitutes the effort of sucking. The air then passes, by its expansibility,
from the vessel into the mouth, as in the barrel of the air-pump. The
communication between the vessel and the mouth is then closed by using
the tongue as a valve, and the same again repeated. 4 r
38. Besides the above means of exhaustion by air-pumps, a partial
vacuum may be produced by the increased expansibility of gases by heat.
Thus, the suction of an ordinary plain cupping-glass is produced by ex-
pelling a portion of the air by heat, by holding it with the mouth down-
ward over a spirit lamp or a piece of burning paper, and then quickly
placing it on the skin. Another means of removing atmospheric air from
a vessel and thus producing a vacuum, is, by the introduction of a volatile
liquid and the application of heat to it, by which it is converted into
vapor, which will expel the atmospheric air. By then closing the vessel
and allowing the vapors to condense, a vacuum is produced, which is
entirely free from atmospheric air, but always contains more or less vapor.
Thus, thermometer bulbs, and other vessels with very narrow mouths, are
filled with mercury or any other liquid, by first expelling a portion of the
atmospheric air by heating them over a spirit-lamp^ and then inverting
them with the mouth into the liquid. When the .air then contracts, a
partial vacuum is produced, by which a portion of the liquid is forced
up into it by the atmospheric pressure (59). They are then again
heated till the liquid inside boils, and its vapour has expelled all the re-
maining atmospheric air, when they are again inverted with the mouth
into the liquid, by which they become entirely filled with the liquid as
soon as the vapors condense. The vacuum in the cylinder below the
piston of the early or ' atmospheric' steam-engine of Newcomen, was pro-
duced by the expulsion of the air by steam from a boiler, and its subse-
quent condensation.
S """39C Compressibility and Elasticity of gases. From the nature of gases
it might be inferred, that the atoms are not so close together as in liquids
27
28 BOYE'S INANIMATE MATTER.
and solids. Indeed, we find that the spaces between their atoms are
capable of being considerably reduced by mechanical pressure and their
volume in consequence diminished. This property is called Compressi-
bility. The property of offering to the compression a constantly increasing
resistance, and when the pressure ceases, of again resuming their former
volume, is called Elasticity. Gases thus" possess the properties of Com-
pressibility and Elasticity to a much greater extent than either solids or
liquids.
40. This is also the reason why we are capable of forcing a considerable
quantity of gas into a comparatively small space. Contrivances for this
purpose are called Forcing or Condensing Air-pumps. In its simplest
form the Condensing air-pump is identical with the Exhausting Syringe,
see figs. 1 and 2, consisting of a barrel with a solid piston, and furnished
with a two-ways stop-cock, by which it is attached to the receiver, into
which the air is to be condensed, only that in using it, the order of turn-
ing the stop-cock is reversed. For if the piston be pushed in, while the
barrel communicates with the receiver, it is easily seen that the air con-
tained in the barrel must be forced into the receiver. If, now, the
stop-cock be turned so as to shut off communication with the receiver, but
to establish it between the barrel and the outer atmospheric air, the
latter will enter and fill the barrel when the piston is again drawn out.
By repeating the same process, a fresh portion of air is by every inward
stroke introduced into the receiver, the limit being dependent on the
strength of the apparatus and the size of the injurious space (29).
For it will easily be seen, that as soon as the air admitted into the barrel
may be condensed into the injurious space, without acquiring greater den-
sity than the air in the receiver, no more can be forced into it.
41. Instead of the two-ways stop-cock we may, as in the exhausting
air-pump, substitute two self-acting valves of oil-silk, see fig. 10, one v
Fig. 10.
at the bottom of the barrel in the passage leading to the receiver, and
another v t in a passage through the piston, both, however, opening
inward as represented in fig. 10. The valve in the piston may be dis-
pensed with, and the latter remain solid, if the barrel be furnished with a
28
PNEUMATICS.
29
small perforation on its side, at a distance from the cover just sufficient to
be cleared by the piston when drawn out, for the admission of atmospheric
air. On pushing the solid piston in, the air thus admitted into the barrel
is confined as soon as the piston has passed the orifice, and forced into the
receiver, and so on.
42. Where larger objects are to be placed in the receiver, the latter
must be furnished with a wide mouth, see fig. 12, the edge of which is
Fig. 11.
ground true and fitted on a plate as for exhaustion, but generally with the
interposition of a ring or washer of oiled leather. An additional contri-
vance also becomes necessary, to keep the receiver against the plate, con-
sisting of two uprights, I and ?, and a cross-piece m, which can be screwed
down on it, as otherwise the inner pressure of the air would force them
apart. Such receivers should also be made as much as possible of a
spherical form, and, if of glass, very thick, as much greater strength is
29
30 BOYE'S INANIMATE MATTER.
required to withstand a pressure from the inside than from the outside,
and by bursting accidents are likely to occur.
43. Where considerable quantities of air are to be condensed, the pump
may be made double-acting and its size increased; in which case it be-
comes necessary to work it by machinery. When high degrees of con-
densation are required, it also becomes necessary to substitute metallic
valves instead of those of oil-silk. The pump jig. 7, described in 33?
answers admirably for condensing, if furnished with two additional passages
leading from the valves u and , as represented by fig. 11, which two
passages unite into one, terminating in a knob n, so that, being of lead,
and therefore flexible, it may be connected by a gallows-screw joint m
with the receiver y^. 12, into which the air is to be condensed. In this
use of the pump the other forked tube t, fixed over the valves, opening in-
ward, must of course be left open, so as to allow the atmospheric air free
access through these valves into the barrel. When the piston is moved,
atmospheric air is drawn in through the tube t on the one side of the piston,
while the air on the other side of it is forced into the receiver through the
tube n. Such pump will also answer for transferring and condensing any
gas different from atmospheric air. For this purpose the receiver Jig. 12,
into which the gas is to be transferred or condensed, is first exhausted by
being connected with the pump by the tube t. It is then to be connected
with the pump by the tube n, after the tube t has been connected with the
receiver containing the gas to be transferred, and one stroke been performed
to expel the atmospheric air from the barrel.
44. It has been ascertained by accurate experiments, which will after-
wards be detailed, that the volumes which a gas occupies under different
pressures, but otherwise similar circumstances, are inversely proportional
to the pressures, and the densities of the gas, therefore, directly propor-
tional to them. This law is called, from its discoverer, Mariotte's law.
iquefaction of gases. In regard to their conduct under increased
mres, gases differ materially. Some of them obey Mariotte's law
under any pressure which has yet been applied to them, and are there-
fore called permanent gases. Of these we have six; Oxygen, Hydrogen,
Nitrogen, Bin-oxide of Nitrogen, Carbonic Oxide and Light Carburetted
Hydrogen. Others conduct themselves in a similar manner, obeying
Mariotte's law, only until the pressure has been increased to a certain point,
when they suddenly yield and are converted into liquids. These are
called liguefiable, sometimes compressible, or condensable gases, the latter,
referring mainly to the fact, that this same effect is assisted by the simul-
taneous exposure to cold, or may even in some cases be produced by it
alone. Of the liquefiable gases a certain number are formed from sub-
30
PNEUMATICS. 31
stances existing, under ordinary circumstances, as liquids or solids, and
when filling the space to their fullest extent, will stand no increase what-
ever in pressure or cold, without becoming wholly or in part liquid.
Such gases are called Vapors. As instances of liquefiable gases may be
mentioned Sulphurous acid, liquefiable at a pressure of about 5 atmo-
spheres (1 atm. = 151bs. to sq. in.), and by strong cold alone, and Car-
bonic acid, requiring 38 atmospheres at 32. Of vapors may be men-
tioned vapor of water or Steam.
46. It is supposed that all gases by sufficient pressure would become
liquid, but even should this not be the case, it is evident that no pressure,
however great, could reduce their volume to nothing, which constitutes
their property of Impenetrability.
47. To illustrate the compressibility and elasticity of the atmospheric
air, fix a burning taper on a cork floating on water. Invert a large
tumbler or jar over it, and depress this below the surface of the water. As
the depth to which it is immersed increases, the compressibility of the air
will allow the water to ascend to a greater height into the jar, but its
elasticity will offer a constantly increasing resistance, so that much the
greater portion of the jar will still remain filled with the air and allow the
candle to continue to burn.
48. On this depends the action of the diving-bell, which consists of an
open inverted box filled with air, generally made of cast-iron, and heavily
loaded, so as to sink when let down into the water by a rope, and fur-
nished with thick glass to admit light. The operator is supported on cross
benches near the bottom. As the bell is lowered to a greater depth, the
pressure of the water becomes greater, and the air in consequence more and
more compressed, so that the water ascends higher into it. To prevent the
diver becoming thereby partly immersed in water, and to replace the air,
which becomes vitiated by the respiration and the burning of the light
sometimes employed, it is furnished with a valve and hose, through which
fresh air is forced in, from a boat above, by a forcing pump. By this
means it soon becomes again entirely filled with air, while the vitiated air
is allowed to escape.
49. As. .an application of the condensation of air by the condensing air-
pump, may be mentioned the air-gun, of which the essential part is a
strong metallic receiver, into which atmospheric air is compressed to a
considerable degree by a condensing syringe, which may be attached to it.
Between this receiver and the barrel containing the ball, is a valve, which
by pulling the trigger is struck open, thereby letting out a portion of the
confined air, which propels the ball. In the ordinary air-gun the stock
forms the receiver, and in the cane air-gun the receiver is formed out
31
32 BOYE'S INANIMATE MATTER.
of the hollow space between the barrel and the outer tube forming
the cane.
50. Besides the condensing air-pump, other means are sometimes re-
sorted to for the compression of gases. Thus, vapors are often obtained
in a compressed state by the introduction of a volatile liquid into a con-
fined space, and its conversion into vapors by heat. The steam-boiler is
an illustration of this. The high-pressure steam-engine may be considered
as a single-barrelled, double-acting air-pump attached to it, the barrel being
called the cylinder, but the piston of which, instead of condensing the gas
by its motion, is itself moved by the elasticity of the gas, the vapor of
water, already in the compressed state and let in alternately above and be-
low the piston.
51. Another way of obtaining gases in a highly compressed state, is by
generating them by chemical action in large quantities in a small space.
Fire-arms may be considered as an application of this, the mixture em-
ployed in them for this purpose being the gunpowder. Many gases, such
as carbonic acid, are most conveniently liquefied by the pressure produced
by their own generation in an appropriate apparatus (see Chemistry under
Carbonic acid).
Properties depending on Adhesion.
I N/ 52. The repulsive action between the atoms of the same gas, which
causes the property of Expansibility, we do not find to exist between the
V/ \ atoms of different gases. On the contrary, the atoms of one gas will
allow the atoms of other gases to push themselves between them, and seem
even to assist this action by an attractive force toward them (Adhesion).
Thus, if two vessels, h and cfig. 13, separated by a partition p, be filled,
the upper li with a light gas as hydrogen, and the lower c by a heavy gas
as carbonic acid, and the partition between them be withdrawn, the hydro-
gen will not remain on top, but expand and spread down-
ward through the carbonic acid; and in the same manner
will the carbonic acid rise up, spreading through the hydro-
gen, till they both are evenly diffused through the whole
P z space. This property is called Diffusibility. In virtue of
this property one gas seems hardly to offer any resistance
to the expansibility of another, and gases are therefore
not capable of limiting each other, or of maintaining a
distinct boundary between themselves (like oil and water
among liquids).
Fig. 13. $\ 53. Diffusibility of gases suffers a peculiar modification,
when they communicate with each other through extremely small openings,
32
PNEUMATICS.
83
as through a crack in a glass, or through a porous partition, as when
formed of plaster of Paris, unglazed earthenware, common wood, particu-
larly when cut across the grain, and animal membrane, as bladder, skin,
&c. In all such cases the lighter gas will be found to pass through such
into the heavier, faster than the heavier passes in the opposite direction into
the lighter. Thus, if in fig. 13, the upper vessel h be filled with hydro-
gen, and the lower c with carbonic acid, and the partition p be a plate of
plaster of Paris, it will be found that the hydrogen will pass faster into
c, than the carbonic acid into h } and thus a partial vacuum is produced in
the vessel h, occupied by the hydrogen, and a condensation in c. But after
some time, when the gases become thoroughly diffused through each other,
equilibrium is again restored on both sides of the partition. This may be
illustrated by the diffusion tube b
fig. 14, which is a glass tube open
at the lower end and closed at the
upper by a plug a, of perfectly dry
plaster of Paris. If this be filled
with hydrogen by displacement of
the atmospheric air (see ), so
as to avoid wetting the plaster of
Paris, and then quickly placed
with its open end in a shallow
vessel dj containing water, diffu-
sion will take place through the
Paris plaster, between the hydro-
gen in the tube and the atmo-
spheric air .outside, and the hydro-
Fig. 14.
gen passing out quicker than the atmospheric air passes in, a partiai
vacuum will be formed, by which the water will be forced up in the tube
to c by the atmospheric pressure (see 59), several inches above the level
outside. But after some time it again falls to its former level. This
kind of diffusion, particularly when taking place through animal or vege-
table membranes, is often called by the name of Endosmosis and Exos-
mosis. The velocities with which different gases diffuse themselves, have
been found to be, under otherwise similar circumstances, inversely pro-
portional to the square roots of their densities or specific gravities.
54. The adhesion of gases toward Solids is quite considerable, so that
in many cases it causes them to be condensed in greater or less quantities
on their surface. Thus, it is found that ordinary glass, even when per-
fectly dry to the touch, always contains a thin film of vapor of water con-
densed on its surface. This becomes more perceptible when its surface
C 33
34
BOYE'S INANIMATE MATTER.
is increased by pulverizing it, when the quantity of vapor condensed by it
may be so great as to amount to more than per cent, of its weight.
The same is the case with most other pulverulent or porous bodies, such
as clay, and particularly animal and vegetable substances, as paper,
wood, hair, membranes. Such water is called hygroscopic moisture and
is found to vary in quantity according to the state of humidity of the
atmosphere ( 177 ), and interferes materially in many experiments with
the accurate determination of their weight. , Kecently ignited charcoal
will absorb many times its own volume of different gases, such as oxygen,
and particularly sulphuretted hydrogen and other similar gases or vapors,
which are the cause of offensive odors. On this depends its preserving and
deodorizing properties. The most extraordinary instance of such condensa-
tion of gases is presented by platinum towards hydrogen and oxygen, when in
porous and finely divided states, in which it is called platinum sponge and
platinum black, the latter of which has been found to absorb more than
250 times its own volume of oxygen. By this condensation a subsequent
chemical action is often induced. Thus, oxygen when absorbed by -char-
coal combines after some time with it, forming carbonic acid in its pores;
and hydrogen and oxygen when absorbed together by platinum sponge
unite to form vapor of water, so that platinum sponge when held before a
jet of hydrogen, where it mixes with the oxygen of the atmosphere, will
become heated by the union of the two gases, and ignite the, jet of hydro-
gen. On this depends the Platinum Igniter,
(Jig. 15), which is an apparatus for obtaining
fire, consisting of a self-regulating generator of
hydrogen (see ), which by turning up the
box li y opens a stop-cock and causes the hyd
gen to issue from the jet e } on the platin
sponge Ji and thereby to become ignited.
55. Towards Liquids also, a positive a
tion or adhesion is very manifest, by which the
atoms of gases are drawn in between the atoms
of liquids, which constitutes what is called ab-
sorption or solution of gases in liquids. Thus
all the atmospheric gases dissolve in water in
small quantities, and on the oxygen thus dissolved (about T J n vol. in 1
vol. of the water), depend all gill-breathing animals for their respiration.
Some gases dissolve in considerable quantities in water, as carbonic acid
(1 vol), and sulphurous acid (50 vols). It is, however, often difficult to
draw the line between mere solution or absorption and chemical combina-
tion. Thus, chlorohydric acid dissolves in water to the amount of 418 vols.,
34
ro-
Fig. 15.
PNEUMATICS. 35
and aramoniacal gas to the amount of 500 vols. ; but in these cases a
chemical combination with the water takes place at the same time.
56. When a gas is dissolved in a liquid, and the free surface of this solu-
tion be exposed to, or brought in contact with another gas, or be separated by
a porous partition from it or from a solution of it in a liquid, diffusion will,
in all such cases, take place between them. It is by such diffusion that
by respiration an exchange takes place, through the membrane of the
lung, between the oxygen of the air and the carbonic acid dissolved in
the blood: and that in gill-breathing animals an exchange is effected,
through the membrane of the gill, between the oxygen dissolved in the
water and the carbonic acid dissolved in the blood. This is also the cause
why, when gases are separated by liquids in which they are more or less
soluble, an exchange of them always takes place by diffusion through the
liquid. This is not only the case when a gas is confined by a very thin
film of liquid, for instance, when enclosed in a soap-bubble; but even
when gases are kept in jars, placed with their mouth in water, it is found,
that in the course of time more or less of an exchange takes place
through the water with the atmospheric air outside. Thus, if the gas be
hydrogen, in the course of some weeks, some of it will have escaped
through the water, while a perceptible quantity of atmospheric air will
have found its way through the water into the hydrogen. As gases are
utterly insoluble in mercury, this liquid is often employed for confining
them more perfectly, and answers well when the surfaces of the glass and
the mercury are perfectly clean. But if a film of dust cover the glass or
be on top of the mercury, when immersing the mouth of the vessel into
it, so as to prevent perfect contact between the glass and the mercury,
diffusion will take place through this film.
Properties depending on Gravity.
57. Gases are subject to the action of gravity, and they are, therefore,
like all other ponderable matter, attracted by the earth towards its centre,
which constitutes their weight. To prove this, attach a spherical receiver
furnished with a stop-cock, to an exhausting air-pump, and having removed
the air, counterpoise it on a balance, see fig. 16, so as to produce equili-
brium. Allow then the atmospheric air to fill the receiver by opening the
stop-cock. It will be found that the receiver now weighs more. This
gtin is due to the weight of the gases which now fill the receiver. By
forcing more air into the receiver by the condensing air-pump, we shall
find that its weight is still further increased. By accurate experiments it
has been found, that 100 cubic inches of atmospheric air, freed from its
35
36
BOYE'S INANIMATE MATTER.
carbonic acid and vapor of water, at 30 inches barometric pressure and 60
Fahrenheit, weigh exactly 30.82926 grains, (or at 32 Fah. 32. 58685 grs).
58. Different gases have different weights for the same volume. Thus,
100 cubic inches of oxygen weigh 34.19 grains, of hydrogen 2.14 grains, of
carbonic acid 47.14 grains. By the density or specific gravity of a gas we
understand the number which expresses, how many times a gas is heavier
Fig. 16.
than the same volume of atmospheric air, which is, therefore, the standard
of comparison and its specific gravity = 1. To obtain the specific gravity
of a gas, we first fill a suitable spherical glass receiver, as above, with atmo-
spheric air, freed from its carbonic acid and vapor of water by passing it
through a tube filled with unslacked lime, and ascertain accurately the
weight of the atmospheric air in it. We then again exhaust the atmo-
spheric air and fill it with the gas (see ), at the same temperature and
at the same pressure, and ascertain its weight. The weight of the gas
divided by the weight of the atmospheric air will then give us its specific
gravity. The following are the specific gravities of some of the different
Atmospheric air 1.0000 Nitrogen 0.97137
Oxygen 1.1056 Carbonic acid 1.529
Hydrogen 0.06926 Vapor of Water 0.622
To avoid fractions the specific gravity of atmospheric air is often called
1000 instead of 1, that of oxygen then becomes 1105, hydrogen 69, &c.
* 59. As gases possess weight, it follows that the surface of the earth
36
PNEUMATICS.
37
must sustain a considerable pressure from the weight of the surrounding
atmosphere resting on it. To prove this, place an open glass tube with
one of its extremities in water, see fig. 17, and remove the air which it con-
tains by suction with the mouth, or by an air-pump attached to the other
end a. We shall find that as the air is removed, the pressure of the atmo-
sphere on the water outside the tube will force it up into it. On re-
admitting the air into the tube the water will again fall to its former level.
For the same purpose expel the air from a tube closed at one end, by filling it
with water \ invert it, keeping the finger on the open end to
prevent the water from escaping, and introduce this end into
a vessel with water. On removing the finger the water does
not run down, but the tube remains filled with the water to
the top, caused by the pressure of the atmosphere on the
water outside of it. As soon as the air be again in any way
admitted into the tube, the water will fall as before. If we
perform the same experiments with mercury instead of water,
and use a tube longer than 30 inches, we shall find, that on
removing the air from the inside, the pressure of the atmo-
sphere on the outside is not capable of forcing the mercury
up to the top of the tube ; or of retaining it there, if closed at one
end and filled and inverted as before, but only at the perpendicular height
Fig. 18. Fig. 19.
37
38 BOYE'S INANIMATE MATTER.
of about 30 inches above the level of the mercury outside, see a fig. 18, and
at which level, therefore, the mercury will remain, whatever inclination
we give the tube, as represented at a a lt a 11 fig. 18. That it still is the
pressure of the atmospheric air outside, which sustains the mercury in the
tube, may be further proved by placing the whole under an appropriate
pneumatic receiver, see fig. ,19, and exhausting the air, when the mercury
in the tube will be found to fall as the air is withdrawn from outside of it;
and if it were possible to remove the air perfectly, the level inside and out-
side would be the same in this case, as when the atmosphere is both in-
side and outside. As water is 13.6 times lighter than mercury, the atmo-
spheric pressure is capable of forcing it up to a height 13.6 times greater
than that of the mercury, or to about 34 feet.
o 60. The pressure of the atmosphere was discovered by the circumstance,
that some Italian pump-makers had in vain endeavored to raise water by
a suction-pump to a greater height than 34 feet, and applied to Galileo for
the reason. Previously, the cause of water rising in a tube under such
circumstances had been ascribed to what was called the abhorrence of
nature to a vacuum, by which nature always endeavored to fill it up.
Galileo referred the subject to his pupil Torricelli, who at once suspected
the real cause to be the pressure of the atmosphere consequent to its weight,
and to convince himself of the correctness of the above facts in regard to
water, performed (about 1643 A. D.), the experiment of filling a tube longer
than 30 inches with mercury and inverting it in a cup of mercury. Such
apparatus is yet called after him a Torricellian tube. The real proof,
however, of the mercury in the tube being supported by pressure from the
atmosphere, was obtained by Pascal having it carried up a high mountain,
by which the air underneath became incapable of pressing on the mercury,
and this therefore gradually fell as the height became greater.
61. The Torricellian tube furnishes us with the means of estimating the
pressure of the atmosphere on the surface of the earth, which for the
greater part, though not entirely, depends on the weight of the atmo-
sphere. For this purpose it is only necessary to measure accurately the
perpendicular height of the mercurial column, this being the only part
of it which is sustained by the atmosphere, the rest, when inclined being
supported by the sides of the tube. This height will be found, as before
stated, to be about 30 inches. The pressure of the atmosphere on Ifce
surface of the earth is therefore equal to a layer of mercury all over it 30
inches in height. We therefore only need calculate the weight of a
column of this height and of a certain base, in order to obtain the pressure
of the atmosphere on an area equal to this base. We thus find, that a
column of mercury, which has the height of 30 inches and rests on a base
38
PNEUMATICS. 39
of one square inch, contains 30 cubic inches of mercury and will weigh
14| pounds, which is therefore the amount of the pressure of the atmo-
sphere on every square inch of surface. The mercurial column in the
Torricellian tube does not, however, always remain the same, but is found
to vary in the same place at different times about 3 inches. The pressure
of the atmosphere is, consequently, not uniform, but varies to the amount
of 1 J pound on the square inch. In most calculations it is considered as
being equal to 15 pounds to the square inch, and in the estimation of
pressures this is considered as a unit under the name of one Atmosphere,
so that for instance a pressure of 3 atmospheres means a pressure of 45
pounds to the square inch.
62. If the Torricellian tube be prepared with care so as to expel all the
atmospheric air and moisture, which adhere to the tube, and which is done
by boiling the mercury in it before inversion, it will easily be seen that
the vacuum produced above the mercury by the subsequent inversion,
must be entirely free from any of the gases of the atmosphere. Hence,
this space is called the Torricellian vacuum, in contradistinction to the
vacuum which may be produced by an air-pump. At the temperature
between 60 and 80 Fah., it begins, however, to contain a perceptible
of vapor of mercury.
THE BAROMETER.
63. As the pressure of the atmosphere varies, it becomes important to
estimate at any time its amount with accuracy. Instruments constructed
for this purpose are called Barometers, from ftapoq (baros) a Greek word
signifying weight, and perpov (metron) measure, meaning literally mea-
surer of the weight of the air (see 90 ). In the ordinary form it consists
of a carefully prepared Torricellian tube (60), inverted in a very small cup
or cistern containing mercury, and furnished with an accurate scale, by
which we are able to read off at any time the height of the mercurial
column above the level of the mercury in the cup.* This is called the
cup or cistern barometer, see Jigs. 20 and 32. In order to fix the tube to
* In the making of accurate barometers certain precautions are necessary in the filling
of the tube. By keeping, more or less dust always finds its way into open tubes. Ba-
rometer tubes should therefore, if practicable, be sealed at both extremities immediately
after they have been drawn at the glasshouse, and be kept in this state till ready for use,
when one end is cut off. Where this cannot be done, it may become necessary to wipe
them clean inside by a thin copper wire, wrapped over with dry thread. Should it be
found indispensable to clean them with water, this is best removed by rinsing with strong
39
40
BOYE'S INANIMATE MATTER.
the cup, the latter may be furnished with a cover of wood, cut across the
grain, by which it is sufficiently porous to let the atmospheric pressure
through it, without allowing the mercury to be spilled out of the cup, and
through which cover the tube may then be fixed (fig. 32), or the whole
cistern may be made of wood, as in fig. 20, the top being in one piece
with it, and the bottom screwed on before inverting it. Instead of
having a cup attached to the
tube, the tube may be bent at
the lower extremity so as to
have the open end turned up-
ward, see fig. 21, in which case
this open end acts as the cup,
and it is then called a plain
syphon barometer, or if the
open end be blown into a bulb
or cup, as in fig. 22, it is called
a syphon cup-barometer. The
whole apparatus is then fast-
ened to a board, Jigs. 21 and
22, or enclosed in a case of
wood or brass, figs. 28 and 32,
on which the scale is fixed.
The whole scale is, however.,
rarely affixed to the barometer,
but only so much of its upper
portion, as is necessary for the
intended use; on ordinary baro-
Fig. 20.
Fig. 21.
Fig. 22.
alcohol, after which the tube is dried by heating it on the outside at a short distance from
one of the open ends, and drawing dry air through it by suction from the other end. As
it is almost impossible to remove any moisture in the tube after it has been sealed at one
end, the greatest care should be taken to avoid introducing any by the breath, or by the
flame of the blowpipe lamp. The sealing should therefore be done by drawing the tube
out at such a distance from the end as to prevent this. Before filling, both the tube and
the mercury should be strongly heated, and in some cases it may even be necessary to
heat the mercury to boiling after its introduction into the tube. The mercury employed
should be purified. This is generally done by forcing it through skin and by digesting it in
a lukewarm place with muriatic or diluted sulphuric acid. For standard barometers it
should be distilled. Distilled mercury is apt to become covered with a black film at the
open end, but this is prevented by subsequent digestion with strong muriatic acid and
thorough washing with water to remove the acid. Syphon barometers are filled with the
mercury as high up as practicable before bending them, after which the filling is com-
pleted through the open end by suitable manipulations. Barometer tubes contracted at any
point to capillary dimensions must be filled in the same manner, as thermometer bulbs (3S)
40
PNEUMATICS. 41
meters seldom more than 4 or 5 inches. In all cases, whether cup or
syphon barometer, the height of the mercurial column is measured by the per-
pendicular distance from the level of the mercury in the open part to the top
of the mercury in the closed end of the tube.
- 64. All barometers have the inconvenience, that when the mercury in
the upper closed end of the tube rises or falls by a variation in the pres-
sure of the atmosphere, a portion of the mercury is either abstracted from,
or added to the mercury in the open part, by which the level of this latter,
which forms the beginning of the scale, is altered. In the cup-barometer
this error may be diminished sufficiently for ordinary purposes, by making
the upper part of the cup, where the mercury rises and falls, see g fig. 20,
of a considerably larger diameter than that of the tube at the upper level
of the mercury. Thus, if the diameter of the cup be 10 times greater than
that of the tube, their relative contents, which are proportional to the
squares of their diameters, will be as 100 is to 1, and therefore a fall of
one inch in the tube will only raise the level in the cup y-J^ of an inch.
Where, however, the utmost accuracy is required, it becomes necessary to
avoid this error altogether, which is done, either by making the scale
movable and adjusting its lower end to the level of the mercury in the
cup, or by furnishing the cup with a movable bottom of skin, which may be
raised by a screw, see h fig. 32, by which the mercury may always be ad-
justed to the same level. This level is sometimes indicated by a float in
the mercury, the stem of which passes through the cover, but more fre-
quently, and with greater reliance, by a point of ivory projecting down
from the cover of the cup, see fig. 32 at p, the cover being made of wood cut
across the grain, so as to allow the air free ingress through its pores, and
the sides of the cistern of glass, so that the point is visible through it. To
adjust the level of the mercury in such cistern before making an observa?
tion, the mercury in it is raised by the screw at the' bottom, till the ivory
point, by dipping into the mercury, forms a small cavity in its surface; it
is then lowered till this cavity just disappears.
65. In the plain syphon barometer, Jig. 23, the above inconvenience
may be avoided by having the bore of the two limbs of the tube of exactly
the same diameter or calibre. It will then be seen, that when the mercury
in the closed end rises, for instance, i inch, it must fall exactly the same
amount, or inch, in the open end; and thus the difference between the
two levels will be one inch. In the same manner all changes of the ba-
rometer will always be double that indicated in the closed end, so that if
the barometer be correct at 30 inches, it is only necessary to double the
value of the other divisions of the scale, that is, half an inch above is
marked 31 inches, and half an inch below, 29 inches, and so' on. As,
41
42
BOYE'S INANIMATE MATTER.
however, it is extremely difficult to obtain the bore of the two limbs
Fig. 23. Fig. 24. O f exactly the same diameter, any uncertainty
I 1 ffi arising from a variation in their calibre, may be
avoided by drawing an arbitrary horizontal line,
see a Jig. 24, between the upper and lower level
of the mercury, and furnishing each limb with a
separate scale, which two scales, s and s, measure,
the one the distance from this horizontal line to
the level of the mercury above it in the closed
limb, the other the distance from this same line
to the level of the mercury below it in the open
limb, which two measures added together will
give the true height of the whole column.
66. A great object in a good barometer is to
be able to measure with accuracy small changes
in the pressure of the atmosphere. But on
account of the high specific gravity of the mer-
cury, being nearly 11000 times heavier than
atmospheric air, these changes are only indicated
by extremely small changes in the mercurial
column. To remedy this inconvenience, so as to
increase the actual motion or sJiow of the barome-
ter, different means have been proposed. As the first of these, may be men-
tioned the substitution of a specifically lighter liquid instead of the mercury,
But in the same proportion as the specific gravity of the liquid becomes less,
the barometer becomes longer and less portable. In the Koyal Society
of London, there is a barometer which was constructed by Daniell with
Water, instead of mercury, the column of which was therefore 34 ft. high,
and varied by the changes in the atmosphere about 3 ft., so as to be
almost constantly in a state of motion. But besides the above named in-
convenience from its size, which would not be an objection for stationary
observatories, all such liquids are liable, if volatile, as water, to evaporate
from the open end, and for the same reason to form a vapor in the vacuum
at the closed end, which varies with the temperature, and of which an
account must be kept; or, if not volatile, as oil, to change by contact with
the air or the sides of the tube.
67. The mercury being thus the only liquid, which can be employed with
advantage in the construction of barometers, it has been attempted to pro-
duce the same effect of increasing its show by attaching certain mechanical
contrivances to the mercurial barometer.
42
PNEUMATICS.
43
68. Thus, in the Diagonal or Inclined Plane Barometer, the upper closed
portion of the tube, in which the mercury rises and falls, instead of being
perpendicular, is inclined so as to form a considerable angle with the per-
pendicular. As the changes of the barometer are measured by the perpen-
dicular height, it is evident, that the mercury in order to arrive at the
same perpendicular height, must travel through a longer distance along
the inclined part of the tube, and thus the motion of the barometer is
increased in the proportion of the hypothenuse of a right angled triangle,
to its perpendicular side, or as the diagonal of a rectangle, to the same.
But as only the perpendicular part of the mercury on the inclined portion
is supported by the atmospheric pressure, the rest being supported by the
inclination of the tube, the friction of the mercury against the sides of the
tube is much greater, and will prevent small changes in the pressure of the
atmosphere from moving the mercury until they become larger, when they
will appear in the above increased proportion. Thus the small changes, which
are the most difficult to observe, are not indicated at all in this barometer.
69. Another barometer constructed with a view to the same advantage,
is the Wheel Barometer (Hooke's), see fig. 25, which consists of a syphon
Fig. 25. barometer, having in the mercury of its open limb,
an iron or glass float, to which is attached a string, that
passes over a small wheel or pulley and is kept extended
by a small weight attached to the other end. The axis of
the wheel is furnished with an index, which traverses
a circular scale. It will easily be seen that when the level
of the mercury changes in the open end, the float will
follow it and by the string move the wheel, and its index
will thus pass over the circular scale, the length of
which must be in proportion to the length of the index/
The graduations on the scale are made to indicate the
corresponding rise and fall of the mercurial column in
inches. Though as regards very small changes, this
barometer is liable to the same objections as the for-
mer, that these are not indicated on account of the
friction of the weight and the pulley, and the rigidity
of the cord ; still for ordinary meteorological purposes
it forms both a cheap and an handsome instrument,
and is therefore often met with in parlors and studies,
as a ' weather glass/ As regards accuracy they are,
however, often made very indifferently, and in such
cases are not reliable for barometrical observations.
44
BOYE'S INANIMATE MATTER.
70. A third barometer of this kind is Huyghen's Double-Barometer,
Fig. 26. Jig. 26. It is a syphon-barometer, the two ends of which are
widened where the mercury rises and falls. The open end
terminates in a long open capillary tube. The mercury of
the barometer fills half of the wide portion of the open end
to a, but the other half of it and part of the capillary tube,
are filled with colored spirits of wine. It is evident, that any
change in the level of the mercury by the pressure of the atmos-
phere, will cause a certain quantity of the spirits to be forced
. 30 into, or withdrawn from, the capillary tube, and thus produce
a change in the level of the spirits in the latter so much
greater, as its relative capacity is less, which change may be
magnified to any desired extent by diminishing the diameter
of* the capillary tube. It has, however, been found that the
spirits is apt, by its greater adhesion to the glass, to work its
way between the mercury and the tube into the vacuum at
the closed end, and thus render it liable to get out of order.
71. All these contrivances for increasing the actual motion
or show of the mercurial barometer have therefore been
abandoned for very accurate scientific purposes, and, instead
of them, increased power and accuracy of observing and
measuring have been substituted. For this purpose the scale
of the barometer is furnished with a sight, or horizontal line, which the
observer may slide along the tube until, by looking over it, he may bring
the top of the mercury on the same horizontal level with it, and thus trans-
fer the level of the mercury to the exact point on the scale, which corres-
ponds to it. On account of the difficulty to the eye to count small divi-
sions, the scale is rarely divided into smaller parts than tenths of an inch,
or at most, the tenths are again divided into halves, or T ^ths. As on this
account the point transferred will rarely coincide with a division of the
scale, a vernier is attached to the sight, in order to measure the exact dis-
tance of the point from the nearest division of the scale.
""72. The Vernier see v v t fig. 27, is a short scale sliding on the main scale,
the use of which therefore is, when a point does not coincide with a division
of the main scale, to measure its distance from this division. To obtain this
distance, one of the extremities of the vernier, either its zero or its highest
number, is placed at the point in question, and the vernier then gives its
distance from the last counted division on the main scale by a fraction,
which has for its numerator the number of that division of the vernier,
which coincides with a division on the main scale, and for its denominator
the whole number of divisions of the vernier, multiplied by the denoniina-
44
PNEUMATICS.
45
27.
tor of the value of the smallest divisions of the main scale. The vernier
is always fixed in such manner to the sight, that when the latter is brought
on a level with the top of the mercury, the nearest extremity of the ver-
nier (either its zero or its highest number) is made to indicate the exact
point on the main scale, which corresponds to the top of the mercury. If
this then coincide exactly with a division on the main scale, this division
is counted and the vernier is not used. But if the extremity of the ver-
nier do not coincide with a division on the main scale, we first count or
read off the height to the nearest lower division on the main scale, and add
to this the distance from it to the extremity of the vernier, which distance
is obtained, as stated before, by looking along the vernier, to find the divi-
sion on it, which coincides with a division on the main scale. Thus, let
1 1 Jig. 27 represent a section of a portion of the tube of a mercurial baro-
meter, with its scale s s divided into
inches and tenths of inches, a the
top of the mercury in the closed
limb, and v p the sight transferring
its level to the scale s s at p } being
also the zero-extremity of the ver-
nier v v . It is evident that the
nearest lower division on the main
scale is 30.1 inch, and the height
to the point p, therefore, 30.1 inch
-f- the distance from 30.1 to p.
This distance is then given by the
vernier to be T J^j of an inch, 7
being the number of the division
on the vernier, which coincides with .
a division on the main scale, taking
this number as the numerator, while
the denominator 100 is obtained by
taking the whole number of divisions
of the vernier, 10, and multiplying
it by 10, the number which is the de-
nominator of the value of the small-
est division of the main scale (J o<;
(hupsos), height, and [usrpov (metron), measure). If the atmo-
sphere were of uniform density throughout its whole extent, the height
of the mercurial column in the barometer would afford us an easy
means of calculating the perpendicular height of the whole atmo-
sphere, or of any part of it, from the known laws of Hydrostatics, that
the heights of columns of different liquids, equilibrating each other
in communicating tubes, are inversely as their specific gravities. Hence
it would only be necessary to multiply 80 inches by 11000, which is
the number expressing how many times mercury is heavier than air,
E 65
66 BOYE'S INANIMATE MATTER.
in order to obtain the height of the whole atmosphere in inches, which
would mate it about 5.12 miles; and in the same manner the perpen-
dicular height of any intermediate part of the atmosphere, between two
places not situated on the same level, would be obtained by multiplying
the difference in the stand of the barometer at these two places by the
same number, 11000. But this is not the case. It has already been
stated in 27, that from other experience it is known that the atmosphere
extends much farther; and both reason and experience tell us, that as we
ascend into the atmosphere, the strata below are not capable of exercising
any pressure on those above, and that the upper strata, therefore, are sub-
ject to less pressure and consequently have also less density. In this
manner both the pressure and the density of the atmosphere must decrease, as
we ascend from the level of the sea to greater elevations : still, knowing the
exact ratio between the different heights to which we ascend into the
atmosphere, and the decrease in the corresponding pressures, the barome-
ter will yet afford us one. of the most valuable means to ascertain the differ-
^_ -i ences in level of different places.
~~*^$>. To understand the principle on which this is ascertained, it may be
stated, that while the different perpendicular heights above the surface of
the earth, if counted from the upper sensible limit of the atmosphere down
to its lower limit at the- level of the sea, form an increasing arithmetical
progression (1 ft., 2 ft., 3 ft., 4 ft., &c., from the top of the atmosphere),
the corresponding pressures on the barometer form an increasing geome-
trical progression. Between any two such series there is a similar relation
as between the ordinary logarithms and their corresponding numbers, the
logarithms forming an arithmetical series, and therefore corresponding to
the distances from the top of the atmosphere ; while the numbers, to which
they are the logarithms, form a geometrical progression, and therefore
correspond to the barometric pressures. If, therefore, at the same time or
moment, we ascertain in two different places, situated at different heights
or on different levels, the true barometric pressures, that is, the heights of
the mercurial columns, corrected for the influence of the temperature (77),
and then from an ordinary table of logarithms take the logarithms cor-
responding to these two pressures (it matters not whether the pressures be
expressed in English inches or in French millimeters), these two loga-
rithms will indicate the relative distances of those two places from the
upper limit of the atmosphere, and may, therefore, by multiplying them by
a constant number, be made to give these distances in English feet or any
other measure. These distances, deducted from each other, will then, of
course, give the difference in their level, or the height of the one above the
other. To avoid the double multiplication of the two logarithms by the
66
PNEUMATICS. 67
constant, the logarithms may first be deducted from each other, and their dif-
ference multiplied by it, which will then give the difference in their level.
To obtain these distances from what may, with sufficient accuracy for pre-
sent purposes, be considered the upper sensible limit of the atmosphere, in
English feet, the constant number by which we multiply the logarithms
of the true pressures, is 60158.5, the temperature of the atmosphere being
supposed to be 32 Fahrenheit, and the difference between the logarithms of
the true barometric pressures, multiplied by this number, will therefore at
once give the corresponding difference in level in English feet, the tempe-
rature of the intermediate column of atmospheric air being 32.
To facilitate these calculations, tables have been constructed, which give
the different distances from the above assumed upper limit of the sensible
atmosphere, calculated in this manner for all the different barometric pres-
sures. These distances for pressures from 28 to 31 inches will be found
in Table III at the end of 'Pneumatics, page
But the above distances are only correct for the standard temperature
of the atmosphere of 32. As air expands by heat, and thus, with the for-
mation of an additional quantity of vapor of water, diminishes its density or
specific gravity for every degree of Fahrenheit by 0.00222 of its density
at 32, the same mercurial column will, at higher temperatures, counter-
balance a proportionally higher column of air. The temperature of the
atmosphere must, therefore, always be ascertained at the same time that we
observe the pressure, by an accurate thermometer, which has been sufficiently
long exposed to it in a suitable place. Should the temperatures at both
places not be the same, their average is taken as the temperature of the
column of air between them. If then this average temperature be not 32,
a correction must be applied to the above difference in level or height,
which correction is obtained by multiplying the above given expansion of
the atmosphere for 1 Fahrenheit, 0.00222, first, by the number of
degrees which the average temperature of the air is above or below 32,
and then by the above-obtained height for 32, which correction is to be
added, if the average temperature of the air be above 32, and deducted,
if below; or, calling the above height, corresponding to 32, h lt , and
the temperatures of the air at the two places or stations, T and T , the
Cor. for temp, of the air above 32 = -f 0.00222 ( T "{" T i 32) h u ,
Cor. for temp, of the air below 32 = 0.00222 ( 32 T + T * \ h iv
It will be seen that this correction is quite considerable. Thus at a
barometric stand of 30 inches, a fall of ^ inch corresponds at 32 to a
difference in level of 87.2 feet, but at 80, this correction for temperature
67
68 BOYE'S INANIMATE MATTER.
of the air being = -f 0.00222 X (80 32) X 87.2 feet = 9.3 feet, it
will correspond to a difference in level of 96.5 feet.
Two other, but comparatively small, corrections are yet to be applied to
the thus corrected height, on account of the decrease of gravity : 1. from
the poles toward the equator, 2. from the level of the sea upward into the
atmosphere, by which the weight of the mercury becomes less, and the
same column of mercury will thus counterbalance a smaller column of air.
These corrections for latitudes near 45, and for small heights, are often
for ordinary amateur purposes entirely disregarded. They will be given
by Tables IV and V at the end of Pneumatics. The first of them depends,
as stated, on the latitude ; and taking gravity and the consequent weight
of the mercury at 45 latitude as standard or unit, we obtain this correc-
tion by multiplying 0.0028371, first by the cosine of the double latitude, and
then by the last-obtained height, which correction, as indicated by the sign
of the cosine, is to be deducted for latitudes greater than 45, and added
for those less than 45 ; or, calling the obtained height, corrected for tem-
perature of air, \ and the latitude L, this
-Co, for Lat. = 0.0028371 cos. 2 L. A, { ^&ffgEfffr.
If the two places have a sensible difference of latitude, the average lati-
tude is used. The second correction for gravity depends on the height or
altitude itself, and is obtained by first adding to the obtained height the
number 52252, then dividing by the mean radius of the earth, 20886861 ft.,
and then again multiplying by the height, which correction is always to
be added, as on account of the less weight of the mercury, the upper por-
tion of the atmosphere has given too great a column of mercury and
thereby caused too small a difference in pressure. Calling the height cor-
rected for temperature of the air and for the latitude, h 0) the
Cor. for altitude = + ^ + 52252 j,
20886861 fl '
Calling the true height or difference in level of two places, 7i, the barometric
pressures at those places corrected for temperature of the mercury and of the
scale, B and b, the following formula will give all the different operations :
+ 0.00222 (2-i-l-i 32 )
h = (Log. B log. b) X 60158,5 ft. X
1 or
0.00222 (32 --^
1+0.0028371 cos. 2 L
h -f 52252
, "" 20886861
68
IEUMATICS. 69
96. To illustrate the above by an example, we may select the calcula-
tion of the height attained by Gay Lussac in his famous balloon ascension
from Paris in 1804, being the greatest height ever attained in this manner.
Observed height of Barometer Temp, of Merc. Temp, of Air Lat.
In Balloon = 12.945 inch = \ 14.90 = t t 14.90 = T IRO *A/ _ T
At Paris =30.145 inch = 5 1 87.44 = t 87.44r=T
Applying the corrections for temp, of the mercury and of the scale (77), we
obtain the
True height of Barometer
In Ball. = b, + 0.0001001 (32 14. 90) M 1O QM . , ,
1 - 0.0000104 (62-14.90) b\ } = 12 ' 961 meh = b
At Par. = B l 0.0001001 (87.44 32)^ \ 9Q Q8q . , R
1 + 0. 0000104 (87.44- 62; \B\ } = 29 ' 983 mch = B
Log. B = Log. 29.983 = 1.4768747
Log. b = Log. 12.961 = 1.1126365
(Log. BLog. b}= 0.3642382 = Difference of Logs.
Difference of Logs, multiplied by 60158.5
= 0.3642382 x 60158.5 = 21912.03 feet = h
Average Temp, of Air = ii = 51.17
Cor. for Temp, of Air = -f 0.00222 /T+ y i _ 32'
= -f 0.00222 x 19. 17 x 21912.03 feet + 932.52 "
Height of Balloon, cor. for Temp, of Air = 22844.55 feet = h l
Cor. for Lat. = 0.0028371 cos. 2 L. h l
= 0.0028371 cos. 9740' X 22844.55 feet.
= 0.0028371 X 0.1334097 X 22844.55 feet = 8.65 "
Height of 'Ball. cor. for Temp, of 'Air and 'for Lat. = 22835. 90 feet = h
22835.90+52252
= + 20886861 X 22835.90 / e e<= + 82.09
Height of Balloon above Barometer at Paris = 22917.99 feet = h
Add height of Barometer at Paris, above level of sea, 159.78
Height of Ball, above the level of the sea, = 23077. 77 feet,
or 4.37 miles.
By the aid of Logarithms these calculations are considerably facilitated.
69
70 BOYE'S INANIMATE MATTER.
97. To obtain the same differences in level in French metres, the constant
number for multiplying the difference of the logs, of the two true barome-
tric pressures (being in this case generally obtained in millimetres) is 18336.
The expansion of the air by heat and by the addition of vapors, being for
every degree Centigrade 0.004, the correction for temperature is 0.004
m i m o srr\ j rp \
2 - h u = 1QQQ ^u> to be added for temperatures above, and de-
ducted for temperatures below 0, as indicated by the sign of (T -\- TJ ;
the correction for latitude is of course the same, and that for altitude
is + ~6366200 ^ J ^ Q W ^ le fornmla ^ eing
2 (T+TJ
1 T 1000
h= (log B log b) X 18336 metres X 4 1 + 0.0028371 cos. 2 L
' /H-15926
+ 6366200
To obtain these different heights in metres almost entirely by the aid of
Tables, the reader is again referred to Meteorol. Tables by Guyot, published
by Smithsonian Inst. To facilitate the conversion of French metres into
English feet, and of English feet into French metres, Table VI will be found
J*L at the end of Pneumatics.
rVV-*U4, gg By calculating in the above manner the height corresponding to a
y ' barometric pressure of 15 inches, we obtain the height of about 18000 feet
or 3.4 miles as that, at which the density of the atmosphere is only one-
half of its density at the level of the sea ; and as the densities increase in
the same geometrical progression as the pressures, it follows that if we
leave out of consideration the effect of the rapid diminution of the tempe-
rature of the atmosphere as we ascend higher, both the pressure and the
density of the atmosphere ought to become one-half less for every addi-
tional 3.4 miles.
99. For the estimation of the difference in level of two places from the
barometric pressures, only the most accurate instruments, such as the
Levelling Barometer described in 81, fg%. 32 and 33, should be used. As
the barometric pressure of the atmosphere is constantly changing, it is neces-
sary to observe the pressures at the same moment in both places, for which
purpose, therefore, two instruments are required, the moments for observ-
ing being indicated by signals or by chronometers. Where this cannot
be done, and the two places are at no very great distance from each other,
the observer may travel with his instrument from the one place to the
other, and then immediately back again to the first station, and if any
change has occurred, take for this station the average of the two observa-
70
PNEUMATICS. 71
tions. If the two places are very distant from each other, the average
stand of the barometer, derived from observations for a length of time,
also affords data from which the difference in their level is often estimated.
As the ordinary variations of the barometer, leaving out the extremes,
which occur only at considerable intervals, rarely exceed even in moderate
latitudes 1J inch, and become much less as we approach the equator (93),
observations with the barometer, performed on a single journey over a
mountainous country, where therefore the differences in the elevations and
the consequent differences in the barometric pressures are very great, will
afford data sufficiently accurate for an approximate estimation of these
elevations; and the barometer is therefore the instrument commonly
employed for this purpose, the form combining the greatest portability
with sufficient accuracy being that of Gay-Lussac's, described in 79. The
Boiling-Point Barometer described in 87, though less accurate, has
been found to give available results. The Aneroid and Metallic Barome-
ters, being the most portable of all, have not yet been sufficiently tested for
such purposes.
100. For estimating the true volume of gaseSj and from it, their weight.
Another use of the barometer, for which it is constantly required in a che-
mical laboratory, is in estimating the weight of a gas from its volume. As
the volume of a gas varies with the pressure on it, it becomes necessary,
when its volume is observed for the purpose of estimating its quantity or
weight, to note the pressure by which it is confined, and then to reduce
the observed volume to what it would be at a standard pressure, which is
assumed at 29.9218 inches of mercury (760 milimetres), this being the
average stand of the barometer at the level of the sea at 45 latitude (93),
and which number is used for all important estimations, serving as a basis
for other calculations, such as the exact weight of 100 cub. inch, of air
(57), but for most ordinary purposes 30 inches is taken as sufficiently"
accurate. Suppose, thus, that the volume of a gas, confined in a gradu-
ated glass tube by mercury or water contained in a pneumatic cistern ( ),
be found by the graduation of the tube to be 24 cubic inches, when the
barometer stands at 29 inches, the level of the confining liquid being the
same inside the tube as outside. We then have by Mariotte's law (44), that
24 cubic in. (vol. at 29 in.) : x (vol. at 30 in.) : : : -QTT
UO OU
29
therefore: x = 24 cubic in. X gn =23. 2 cub. inches
which is the volume the gas would occupy at the standard pressure of 30
inches. If the level of the confining liquid should not be the same inside
the tube as outside, but for instance higher, this column, being supported
71
72 BOYE'S INANIMATE MATTER.
by the atmospheric pressure, must of course be deducted from its pressure
on the gas. Thus, suppose the confining liquid to be water, the volume of
the gas, as before, 24 cubic inches, and the barometer 29 inches, but the
water inside the tube 2.9 inches higher than outside. By dividing the
latter by 13.6 (the specific gravity of mercury), we find this column of
water to be equivalent to 0.21 inch of mercury, which, deducted from
the observed atmospheric pressure of 29 inches, leaves 28.79 inches of mer-
cury, as the pressure on the gas; 24 cubic inches, at 28.79 inches' pres-
sure, are then reduced to the standard pressure of 30 inches as above, by
multiplying by the former (the observed pressure), and dividing by the
28.79
latter (the standard), = 24 cubic inches X ~gQ= 23. 032 cubic inches.
In the latter case, however, where a gas is measured over water as confining
liquid, the thus obtained volume includes the portion of vapor of water,
which is always formed by evaporation and adds its volume, which depends
on the temperature, to that of the gas. To avoid this error, it is only
necessary, in reducing the observed volume to the standard pressure, to
deduct from the atmospheric pressure also that portion of it, which is sus-
tained by the tension of the vapor, and which is obtained by taking from
Table IX, the maximum tension of vapor of water corresponding to the
observed temperature of the gas. Thus, suppose in the above case, the
temperature of the gas to be 79 Fah., we then find from Table IX that
the maximum tension of vapor of water corresponding to this temperature,
is 0.99 inch. From the whole pressure of the atmosphere, 29 inches, we
then deduct, not only as before, the portion sustained by the column of
water above the level outside, equivalent to 0.21 inch of mercury, but also
that, sustained by the tension of the vapor, 0.99 inch, which thus leaves
only 29 0.21 0.99 = 27.80 inches as the real pressure on the gas.
The volume of this, without the vapor of water, at 30 inches, will there-
27.80
fore be = 24 cubic in. X gQ =22.24 cub. inches.
This volume must then also be reduced to the standard temperature (see
Thermics, under Expansion of Gases), which is assumed in England at 60,
but in most other countries at 32. This is done by multiplying the
volume of the gas by 1 + 0.002178 X Stand. Temp., and dividing it
by 1 + 0.002178 X Obs. Temp* Thus, for the above 22.24 cub. in. of
* If 32 Fah. be adopted as the standard Temp., the reduction to this from any higher
degree t is more conveniently performed by dividing the volume by 1 -}- 0.00203611 (t
32) ; the coefficient of expansion for 1 Fah. referred to the volume at 32 as unit being
22.24 cub. in.
0.00203611. Thus, in this case: 1 , Q QQ203611 (79 32 Q ) ==: 2Q>298 cub<
72
PNEUMATICS.
73
79 temperature, we have its volume at the standard temperature of 32
14-0.002178 X32
= 22.24 cub. in.
=2(X298 Cub ' in '
i + o.002178 X 79
For the true volume V, of a gas, we thus have the following formula,
b 1+0. 002178 X^ 7
V X jf X i_|_o.002178x*
F being the observed volume; 5r=the true (77) barometric pressure,
with deduction, if necessary, for any inequality in the level of the confining
liquid and for admixture of vapor of water ; B= the standard barometric
pressure to which it is to be reduced ; t = the temperature of the gas ;
T= the standard temperature to which it is to be reduced; and 0.00217802
= the expansion for 1 Fah. referred to the volume at as unit.
Having thus reduced the volume of the gas to the
standard pressure and temperature, its weight is then
easily obtained, if it be atmospheric air, by multiplying
the number of cubic inches thus found, by the weight
of 1 cubic inch of atmospheric air of the same stand-
ard pressure and temperature, and which has been
given in 57. If the gas be any other than atmospheric
air, we obtain its weight by multiplying the weight,
thus found for atmospheric air, by the specific gravity
of the gas, referred to atmospheric air as a unit, see
58. Thus, if the above 20.298 cub. in. be Nitrogen,
we have its weight :
= 20.298 cub. in. X 0.325868 grs. X 0.97137
= 6.425 grains.
Experiments to prove Mdriotte's Law.
Fig. 40.
30-
c.
-e
-a
7
of the atmosphere and the means of estimating it, we
may again revert to the compressibility and elasticity
of gases, and describe the experiments, by which the ,
law already stated in 44 was established by its dis-
coverer, Mariotte, after whom it has been called Mari- -
otte's Law. He enclosed a quantity of air in a tube ,
bent as the letter J, or as it is technically termed, in
the shape of an inverted syphon, see fig. 40, the short * ~
limb of which was sealed and graduated into volumes,
\
10-
-a
but the long one left open and furnished with a scale measuring inches.
Mercury was then poured into the open end, so as to fill the bend to 1,
73 7
74
BOYE'S INANIMATE MATTER.
thereby enclosing a certain volume of air in the short limb, without its stand-
ing with a higher level in the open limb. Under these circumstances, the
enclosed air, the volume of which we will call 1, is only under the ordi-
nary atmospheric pressure, say 30 inches of mercury. More mercury was
then poured gradually into the open limb, by which the air in the closed
limb became more and more compressed. The height of the mercury in
the open limb, above its level in the closed limb, was then carefully
observed, and compared with the corresponding volume of the air in the
closed limb itself. It was thus found, that when the air was reduced to
f of its original volume, the height of the mercury in the open limb
above its level in the short limb, from a to a, measured 10 inches, to which
must be added the ordinary atmospheric pressure of 30 inches, in order
to obtain the whole pressure on the gas, making it equal to 40 inches of mer-
Fig. 42. curv or 1 =| Atmosphere's pressure (61).
More mercury was then poured into the open
end, till the volume of the air was reduced
to J, when the height of the mercurial
column, from I to b lt producing this eiFect,
was found to be 30 inches, or 1 Atmo-
sphere, which, added to the pressure of the
atmosphere itself, made the pressure on the
enclosed air 2 Atmospheres. In the same
manner, the column c c , when the volume
was reduced to J, was found to be 90 inches,
which being 3 Atmospheres, added to the
pressure of the atmosphere itself, made the
pressure on the gas 4 Atmospheres. The
different volumes of the air were thus found
to be as 1 : f : \ '- i, while the pressures corres-
ponding to them, were as 1 Atmos. : | : 2 : 4,
that is, the volumes occupied by the air were
inversely proportional to the pressures on it.
102. To prove the same law for smaller
pressures than one Atmosphere, a graduated
straight tube, see Jig. 41, open at its lower
extremity, and furnished with a screw-stop-
per at its upper extremity, is immersed with
its open end into a deep glass jar containing
mercury, until only a certain known volume
of air is left at its upper end. This volume we will call 1. The tube
74
PNEUMATICS. 75
being yet open, and the mercury having the same level inside and outside,
this volume of air must of course be under the same pressure as the rest
of the atmosphere, that is, under 1 Atmosphere's pressure. The tube is
then closed and raised out of the mercury, until the volume of the enclosed
air is increased to double its former volume, see fig. 42. The mercury
will then be found to stand much higher inside the tube than the level
a outside it in the jar. This height, from a to 2, is then measured, and
will be found to be 15 inches, which, being supported by the atmosphere,
must of course be deducted from the ordinary atmospheric pressure of
30 inches, in order to obtain the pressure on the gas in the tube, which,
therefore, will be 30 15 = 15 inches of mercury, = \ Atmosphere.
The tube may then be raised still higher out of the mercury, until the
enclosed air acquires 4 times its original volume, when the height of the
mercurial column, raised above the level outside, will be found to be 22*
inches, which deducted from the atmospheric pressure of 30 inches, leaves
of this only 7 5- inches or \ Atmosphere, as the pressure on the gas. We
thus find in these experiments, the volumes of the enclosed air to be as 1 :
2 : 4, while the pressures are as 1 Atmosphere : \ : i, or, as before, the
volumes are inversely proportional to the pressures.
103. A tube similar to any of the above, closed at one end, and con-
taining a portion of air confined by mercury, is often designated by the
name of a Mariotte's tube.
104. The above experiments have since been extended with atmospheric
air from ^-J^ Atmosphere's pressure to that of 27 Atmospheres (139) and
more, and Mariotte's law confirmed to this extent. But it has also been
found, that this law strictly applies only to permanent gases, and to such lique-
fiable gases as are remote from their point of liquefaction, but that as soon
as they approach the latter, their volume will diminish by increased pres-
sures in a somewhat greater ratio. This has been found to be the case
with Sulphurous acid and several others. In the same manner, even Car-
bonic acid, if cooled to 32, has been found to expand by diminished pres-
sures more than it ought according to Mariotte's law, or more than atmo-
spheric air does. This is probably also the reason, why most compound
liquefiable gases and vapors are found, by experiments, to have a some-
what greater specific gravity than that calculated from the volumes of their
^-v component ingredients.
LV^S ^ ^ Pressure- Gauges.
105. Instruments on the principle of the Barometer or Mariotte's tube,
are often used for measuring the tension and elasticity of gases, or the pres-
sure which they exercise when confined (see 117). Such instruments
75
76
BOYE'S INANIMATE MATTER.
L
are called Pressure- Gauges, sometimes Manometers (see note to 91). Fig.
43 shows, on an enlarged scale, the Mercurial Exhaustion-Gauge, m,
Fig. 43. attached to the double-barrelled Exhausting Air Pump,
fig. 6, to indicate the quantity of air remaining at any time
during the exhaustion, by the tension or pressure which it
exercises, and to which its quantity is proportional. It will
be seen, that it is an abridged or shortened syphon baro-
meter, which is enclosed in a small separate receiver, con-
nected with the passage leading from the barrels a and b
fig. 6 to the large receiver h. From an inspection of fig.
43, it will easily be seen, that the closed limb, being only
12 inches long, will exhibit no Torricellian vacuum, but
remain filled with mercury, to the top, until the tension or
pressure, which the air in the receiver is capable of exer-
cising on the mercury in the open limb, is reduced to 12
inches of mercury, and therefore the density of the air is
only J or f of its original density, f having been removed ;
after which all further rarefaction will be indicated by it,
the amount of air remaining at any time, being given as a
fraction, which has for its numerator the mercurial column
sustained by it in the gauge, and which is measured by the
perpendicular height between the levels of the mercury in
the two limbs as stated in 65, and for the denominator the
whole atmospheric pressure as indicated by the barometer
at the time, and which may be assumed at 30 inches. Thus,
when the gauge indicates 10 inches as in the figure, the re-
maining air is -JJJ = -J of its original amount, and when the
A
gauge indicates -f^ inch, the remaining air is ^ = -3^. ^
106. For measuring pressures larger than the ordinary atmospheria
pressure, Mercurial Pressure-Gauges receive the forms represented in Jigs.
44 and 45. Fig. 44 has the general form of a cistern barometer, but the
cistern c containing the mercury is closed air-tight at the top and made
to communicate with the vessel, in which the gas is confined, by a small
tube, passing from the top, or as a fig. 44, through the bottom to above
the level of the mercury. The tube b is open at the upper end, and the
pressure, therefore, estimated by the height of the column of mercury,
which is forced up in it, for which purpose it is furnished with a scale
measuring inches, 2 inches being equivalent to 1 pound on the square inch.
Fig. 45 exhibits another pressure-gauge, which is easily constructed out of
PNEUMATICS.
77
Fig. 45.
20,,
a glass tube by bending it twice. The pressure is measured by the difference
Fig. 44. between the two levels of the mercury in the two
limbs (65). For measuring very small pressures,
such as that under which ordinary lighting gas is
forced through the burners from the pipes, it is made
to contain water instead of mercury, in which case
for great accuracy the tube should be i inch in diani.
and each limb furnished with a vernier. As the tube
of this kind of pressure-gauges is open towards the
atmosphere, and the mercurial column in it, there-
fore, subject to the atmospheric pressure, it is neces-
sary, in order to obtain the whole tension or elasticity
of the confined gas, to add to the above pressures indi-
cated by the mercurial column in the gauges, the
ordinary atmospheric pressure, but this is often
omitted, and the pressure only given as being over
and above the outer atmospheric pressure.
107. The above mercurial gauges, in which the
pressure is measured by the height of the column of mercury, which it can
sustain, are the most reliable of all, but they have the serious inconvenience,
that when the pressure becomes large, for instance in high-pressure steam-
boilers, where it often exceeds 60 pounds to the square inch, or 4 Atmospheres,
the tube must be more than 4 X^O in. =10 feet long (see 139). For such
Fig. 46. high pressures Condensed Air or Mariotte's Tube Gauges are
often substituted, acting on the principle of estimating the pres-
sure from the volume of a confined portion of air. Any of the
above gauges j%s. 44 and 45 may be converted into such by closing
the upper end of the tube, so as to confine the portion of atmo- '
spheric air which is containe'd in it, which volume is then
divided into fractions. Fig. 46 exhibits a gauge of this kind,
such as is used by gas-fitters to prove by high pressure the
tightness of gas pipes. For small pressures the tube is left
open at the top, and it then acts as one of the above-described
mercurial gauges. When used, it is screwed on the end of
one of the pipes, into which air is forced by a forcing pump.
Any leakage is indicated by the gradual diminution of the pres-
sure. For convenience in the making of it, the cistern c is made of
brass ; but as this is corroded by mercury, the latter is contained in an
iron cup i, placed inside. The cover into which the tube b is cemented,
is made to screw on air-tight. The compressed air, the elasticity of which
77
15. a!*.
/ *
78
BOYE'S INANIMATE MATTER.
X-
we want to measure, finds its way between the cup i and the inside of the
cistern c, so as to press on the top of the mercury, which, being forced up
into the tube b closed at the tipper end, will compress the atmospheric air
which it contains, from the volume of which the pressure is ascertained.
Thus, when its volume is reduced to , the pressure on it is 2 Atmospheres,
or 1 Atmosphere over the ordinary atmospheric pressure ; when compressed
to }, the pressure is 3 additional Atmospheres over the ordinary atmo-
spheric pressure ; when compressed to $, 7 additional Atmospheres. To
these pressures must, however, be added, in order to find the pressure or
elasticity of the confined gas, which we want to measure, the column of
mercury inside the tube above the level in the cup i. Thus, if the height
of this be 6 inches, when the volume is J, the elasticity of the confined gas
is g^j = -J Atmosphere more than indicated by the volume of the air in
the tube, or altogether 1-j-J Atmosphere, = 36 inches of mercury, or 18
pounds to the square inch; if 9 inches, when the air is compressed to ,
Fig. 47. the whole pressure is 3-}~3 9 o Atmospheres; if 10 inches,
10J
when compressed to J, 7-f gQ~ 7 gj Atmospheres, &c.
It is a matter of course, that if the temperature be not
constant, its effect on the confined air in the tube must also
be taken into consideration, by first reducing its volume to
the same temp., as in 100.
108. Condensed air pressure-gauges, besides being
considerably affected by the temperature, have also the
great objection, that as the pressure increases, and it in
many cases becomes important to estimate it with increased
accuracy, the divisions of the scale, corresponding to the
same increase in pressure, diminish very rapidly in size,
and thus become less accurate. This latter may, how
ever, be partly remedied by furnishing the gauge with two
tubes, see fig. 47, as first contrived by Dr. J. K. Mitchell
in his experiments on the liquefaction of carbonic acid.
The second tube b is enlarged at the end which dips into
the mercury, by being cemented into a short iron tube d
of larger diameter, which forms its lower extremity and the
capacity of which is such, that the mercury only enters
the glass tube ate, when the pressure approaches that which
we particularly want to measure. Thus, suppose that the
mercury in d only reaches to e, when the air in a is com-
pressed to | its original volume, and that then the mercurial column in it is 36
78
-13
PNEUMATICS. 79
inches above the level at c. The pressure measured will then be 9!
Atmospheres. Deducting from this the column from c to e, the pressure
on the air in the tube b will be exactly 9 Atmospheres. If this volume of
the tube above e be divided into fractions, it is evident that when the
enclosed air is reduced to J of this volume, the pressure on it will be 18
Atmospheres, and when reduced to i, 36 Atmospheres; to which, of course,
in order to obtain the pressure we want to measure, must be added the mer-
curial column beyond e.
109. For experiments on a small scale, as for the compression of gases
in glass tubes, a capillary tube of the proper length, see a b fig. 48, is
Fig. 48. employed as a gauge, having no cistern.
^_ -4- Jk-tc^ Being closed at one end at a, a small
& c ' a column of mercury c is introduced into
the other open end b, by expelling from it, by heat, the smallest possible
quantity of air, and then dipping the open end into mercury, till on
cooling a small quantity of this is drawn into it (38), which then con-
fines the air remaining in the tube. The space ac occupied by this air is
then divided as before into fractions of its own volume. When using it,
the open end b is either cemented into a metallic socket, which is screwed
on to the end of the tube in which the gases are compressed, or in some cases
the whole gauge-tube may be slipped into the compression-tube, in which
case no strength is required of its sides, and these may therefore be of any
thinness, and the whole gauge, therefore, of miniature dimensions. If this
gauge be in a horizontal position, no allowance whatever, need be made for
the weight of the mercurial column c; and the volume of the confined air,
therefore, indicates the whole tension of the gas which we want to measure.
110. Gauges for measuring high pressures are particularly required for
high-pressure steam-boilers, to indicate at any time with accuracy the ten-
sion or elasticity of the steam, and thereby to warn against accidents.
Such gauges are called Steam- Gauges, sometimes also Manometers, see
foot-note to 91. Besides the before described pressure-gauges, many
others have been constructed for steam-gauges on different principles.
Thus, the principle of Bourdon's Metallic Barometer (89), was first employed
for a steam-gauge, by admitting the steam into its hollow hoop-like vessel.
In the same manner an accurate thermometer will indicate from the temp,
of the steam, its pressure, see 138 &c. A number of steam-gauges act on
the principle of letting the steam act on a metallic valve, so as to compress a
spring (Spring-Gauges), or raise a known weight. These are, however, not
so much for the purpose of measuring the pressure of the steam as for afford-
ing escape and safety from it, when its elasticity should exceed a certain
limit, and they are therefore called Escape or Safety Valves, see 146 Jig. 70.
79
80
BOYE'S INANIMATE MATTER.
iments to illustrate the pressure of the Atmosphere.
Fig. 50.
.. The atmospheric pressure on the surface of liquids, may be illus-
trated by the Fountain or Jet in Vacuo, see fig. 49, which consists of
Fig. 49. a closed receiver, which is furnished
at its lower extremity with a stop-cock
c, from which a jet projects into the
receiver, terminating outside by a screw
s, by which it may be attached to
the air-pump. Having exhausted the
receiver, it is detached from the air-
pump, and the mouth of the stop-cock
immersed into a vessel containing water.
On opening the stop-cock the atmo-
spheric pressure will force the water
in a jet into the exhausted receiver.
112. The Mercurial Ham, see jig.
50, is used to illustrate the same in
connection with the porosity of certain
substances such as wood, leather, &c.
It consists of a receiver having inserted
in the top a cup c, which is closed
at the bottom by a stopper of wood cut
across the grain, or by a piece of buck-
skin, and which contains mercury. On
exhausting the receiver, the atmospheric
pressure will force the mercury through
the pores in small globules as a rain.
113. If a piece of thin bladder be tied over the top of a small wide-
mouthed receiver, the Bladder Glass, see fig. 51, and the air then
Fig. 51. quickly exhausted, the atmospheric pressure will burst the
bladder inward with a loud report as from an explosion.
114. The pressure on any part of an elastic fluid being
equally communicated to all parts of it, it is evident that
the pressure which it in return exercises on all the con-
fining limits must be uniform, and must, therefore, also
extend to the whole surface of any object immersed in it.
The direction of its pressure at any point of all such sur-
faces, is always in the perpendicular to them at that point. The Upward
Pressure of the atmosphere on an under surface, may be illustrated by
80
PNEUMATICS.
81
a syringe with a solid piston, see fig. 52. Having drawn the piston out and
Fig. 52. attached a weight to the piston-rod, suspend it, and con-
' nect the upper extremity of the barrel by the tube a with
an exhausting air-pump. When the air is exhausted from
it, the atmospheric pressure, acting perpendicularly upward
on the lower surface of the piston, will force it up, thereby^
raising the weight attached to the piston-rod.
115. The same may be illustrated by the Magdeburg
Hemispheres, which are two hollow hemispheres, see a and
b fig. 53, having their edges ground true, so as to fit air-
tight together, thus forming a hollow sphere. One of them
is furnished with a handle, and the other with a stop-cock
and a screw c, by which it may be attached either to an
air-pump, or to a handle d. If the two hemispheres be
put together, and the air inside exhausted, the pressure
of the atmosphere outside will force them together, so
that if they be removed from the air-pump, and the handle
attached, it will require a considerable force to separate
them. To calculate the exact force with which they are
held together, it must be remembered, that though the
whole atmospheric pressure on them is equal to 15 pounds
on each square inch of the whole outer surface, it is only
that portion of it which acts at right angles to the plane
of the joint, which holds them together. Thus, if the
radius of the sphere be 2 inches, the plane surface of the
circular joint (r 2 TT) will be = 2 a X 3? = 12| square
inches, and the pressure on it, therefore, 124 x 15 Ibs.
Fig. 53.
=188 1 Ibs. To pull them apart, this force must, therefore,
be applied from each side. They have received their name
from the fact, that they were first contrived by Otto von
Guericke, Burgomaster of Magdeburg, a town in Germany,
who in 1650 had invented the Air-Pump. To illustrate
the Atmospheric pressure, he exhibited, in 1654 at Regens-
burg, to the Emperor Charles Y, in presence of the Imperial
Diet, a pair of these of about two feet in diameter, to which
twenty-four horses were attached, without their beina^rt>Je to
116. The external surface of the human body being about
2000 square inches, it is evident that it must be exposed to
a pressure from the atmosphere, of about 30.000 Ibs., or nearly 14 tons. That
F 81
82 BOYE'S INANIMATE MATTER.
this pressure does not force in the Abdominal and Thoracic cavities of the
body, is prevented by the access of the atmosphere to them, by which the
external and internal pressures are counteracted. The solid walls of the body
forming them, are, however, subject to it; these and the internal organs
are, however, prevented from being crushed by it on account of the uni-
' formity of the pressure, by which the particles, being pressed equally on all
sides, have no tendency to change their relative position, crushing being
merely produced by an unequal pressure. This is also the reason why we
are not conscious of its existence. It may, however, easily be made mani-
fest by removing the pressure from any part of the body, for instance, by
Fig. 54. placing the hand over the mouth of a small
receiver, see fig. 54, and exhausting the air
from within it; the pressure on the opposite
side of the hand will then force it against the
edge of the receiver and cause those parts, from
which the pressure is removed, to bulge into
it. The operation of cupping depends on this
^ same, for if small cuts be previously made
k^j i^ through the skin, the blood will be forced out
through them by the pressure on the rest of
the body. In such places, however, of the body, where the parts are not
soft or permeable to fluids, this pressure is used by nature to sustain and
keep together its different parts, without calling into requisition for this
purpose the power of the muscles. Thus all the movable joints of the
body are kept together by the articulating surfaces of the bones being sur-
rounded by an air-tight ligament, so that they may slide freely over each
other, but cannot be separated without producing a vacuum, and are thus
forced together by the atmospheric pressure, amounting, for instance, on
the knee-joint to upwards of 100 Ibs. By actual experiment, by dissect-
ing away from the hip-joint every thing excepting the capsular ligament,
and suspending it under a pneumatic receiver with a weight attached to
the thigh-bone ; this has been found to drop out of the socket, on exhaust-
ing the air from the receiver, but to return again into it, on re-admitting
the air The excessive fatigue experienced in ascending high mountains,
has been ascribed to the diminution of the atmospheric pressure, by which
the weight of the limbs has to be in part supported by the muscles,
instead of by the atmospheric pressure alone.
f\ Experiments to illustrate the Expansibility, Elasticity and Compressi-
J * & $$'^ bility of Atmospheric Air.
111. Expansibili^and Elasticity of gases both depend on the same
82
PNEUMATICS.
83
repulsive action between the atoms, which we have called negative cohe-
sion (12), and which causes them to have a constant tendency to extend
their volume and thereby to exercise a certain pressure on the confining
limits, which these must return, in order to restrain them ; and as soon as
this restraining pressure is diminished or ceases, it causes them actually
to extend their volume. They are therefore in fact the same property, but
the word elasticity is only applied to their expansive force after a previous
diminution of their volume, by an increase of the pressure of the confining
limits, while for their expansive force under the ordinary atmospheric
pressure, or after its diminution, the word tension is generally used.
Fig. 55.
Fig. 56.
118. The Expansibility of atmo-
spheric air is illustrated by forcing
the greater portion of the air out
of a sound bladder or small gum-
bag by compression, and then
closing the orifice by tying it
firmly with a string. Place it
under a receiver as in fig. 55. As
soon as the air is exhausted from
the receiver outside the bladder,
the small quantity of air con-
tained inside it will expand, and
swell the bladder out, as seen in fig. 56. When
the air is again admitted into the receiver, the
bladder will collapse to its former dimensions.
The same experiment will often succeed with
dried and shrivelled fruit, as raisins, which, if the
skin be sound, will, in a similar manner, be blown
out to their original fullness by the small quantity
of air which they contain.
119. Mechanism of Respiration. It is by a
similar contrivance that air is made to enter into
the lungs by respiration. The lungs may be con-
sidered as two membranous bags, only divided into
a number of smaller compartments or cells, but
all communicating with each other by the bron-
chial ramifications, through which the air may
enter into them by way of the mouth and the
windpipe; the whole apparatus being suspended
in the cavity of the chest, as may be represented by the bladder a fig. 57,
83
84
BOYE'S INANIMATE MATTER.
attached to the pipe b and fixed in the receiver h. The expiration is effected
by diminishing the cavity of the chest by the contraction of the ribs and
the raising of the diaphragm, by which the air, in consequence of its elasticity,
is forced out through the windpipe by compression. This may be imitated
by blowing the bladder out through the pipe I and closing this with the
finger, until the mouth of the receiver be immersed into a vessel e e, with
water. On removing the finger and depressing the receiver further, the
air will be forced out through the pipe 6, as represented in fig. 57. The
inspiration, on the contrary, is effected by enlarging the cavity of the
chest by expanding the ribs and flattening the diaphragm, by which a
vacuous space is produced between the inside of the chest and the mem-
brane of the lungs, by which the air, in virtue of its expansibility, will
enter and innate them. This operation may be imitated with the above
apparatus by gradually drawing the receiver li again out of the water,
thereby enlarging its capacity and producing a partial vacuum. The air
Fig. 58. then enters by its expansibility through the pipe
& and inflates the bladder as in Jig. 58.
120. Common water freshly drawn always
contains more or less air in solution (55).
When the pressure is removed from its surface
by placing it in a tumbler under a receiver and
exhausting the air, the expansibility of the dis-
solved air will overcome the adhesion, by which
it is kept in solution, and most of it will appear
as small bubbles on the sides oL4ke vessel and
escape through the water. I jfyQj\J\$U(/S
121. Place a piece of charcoed or any other
porous body in a tumbler filled with water, and
this under a receiver, and exhaust the air from
the latter. The air contained in the pores of the
charcoal will expand and escape in bubbles
through the water. On readmitting the air, the
atmospheric pressure will force the water into
the pores, which thus will become filled with
water instead of air. This method is often
employed to fill the pores of other porous bodies with water. If the pores
of wood be filled in this manner with water instead of air, it will become
water-logged and incapable of noatinj
an apparatus useBTto illustrate the compressibility,
elasticity and expansibility of atmospheric air. It consists of a strong,
84
PNEUMATICS.
85
Fig. 59. generally spherical vessel, a fig. 59, having a tube in-
serted at the top, reaching nearly, though not quite, to
the bottom, and furnished outside with a stop-cock and
screw for attaching a jet i. A quantity of water suffi-
cient to close the end c of this tube, is introduced into
the vessel, either by unscrewing the tube, or by remov-
ing a portion of the air from it by suction, and then,
after having inverted it and immersed the jet of the
tube into water, opening the stop-cock, when the atmo-
spheric pressure will force in a sufficient quantity of the
latter (111). Remove then the jet and attach to it a condensing syringe
(41). By every stroke of the piston, the air forced into the vessel will
be seen to bubble through the water. Having closed the stop-cock,
remove the condenser and replace the jet. On turning the stop-cock, the
elasticity of the compressed air will force the water out in a jet. Having
replenished, if necessary, the vessel with water, place it under a receiver
and exhaust the air, see fig. 60. By thus removing the pressure of the
Fig. 60. atmosphere on the water inside the jet, the expan-
sibility of the atmospheric air enclosed in the ves-
sel will force the water out in a jet. Hero's ball
is so called from its inventor, who lived in Alex-
andria, and described this apparatus about one
hundred and twenty years before the Christian
era.
123. Contrivances acting on the same principle
as Hero's ball, and called Air-Chambers, are
attached to most hydraulic engines, such as the
Fire Engine and the Hydraulic Ram, in order to
convert the intermitting jet of these into a con-
tinuous. The air-chamber consists of a strong,
more or less spherical vessel of metal, at the bot-
tom of which the water is forced in through a valve faster than it issues from
the jet, which may either pass from near the bottom through the top, as
in Hero's ball, or, as is more common, from the side near the bottom. The
air enclosed in the chamber is thus compressed and, by its elasticity, forces
J;he water out in a constant stream,, /]
npa^Tanddnertia of Gases, f
124. Gases, like all other matter, possess Inertia; hence the atmosphere
offers a resistance to all bodies moving in it, because these have to impart
85 8
86
BOYE'S INANIMATE MATTER.
to it by impact some of their motion, in order to move it out of their way.
For this reason, bodies which present a large surface, lose their motion
sooner than those which present a smaller, or one of a more favourable
shape. In the same manner, specifically light bodies lose their motion
sooner than heavy bodies, which within the same space contain more
moving matter and, therefore, more motion. This may be illustrated by
the Windmill experiment, which is performed by an apparatus, see Jig. 61,
having two axes i i, perfectly alike, and fur-
nished with small pinions, that are worked by
two perfectly similar racks r r, attached to
the same weight w, so that the latter by its
descent imparts exactly the same velocity to
them both. At right angles to each of the axes
i i, are attached four perfectly similar wings,
which may be turned so as to present either
their broad surface or their edge to the air,
when the axes revolve. Place first the wings
of both axes, so as to present the broad sur-
face to the air, when revolving. Let then
the weight drop so as to impart to them both
the same velocity. They will both stop at
the same time, arid soon, on account of the
resistance of the air. Turn then the wings
of one axis so assto present the edges to the
air, and start them again by the descent of the
weight. The one with the wings turned
edgeways will then continue its motion much
longer than the Other. But if the apparatus
be placed under^ an exhausted receiver, and
the weight again made to descend by the
rod g g, passing through a stuffing-box s at the top of the receiver, both
axes will be found to continue their motion equally long in the vacuum,
r lilthough the wings of the one are turned differently from those of the other.
125. The resistance of the air by its inertia, is the cause why specifically
lighter bodies fall in the atmosphere slower, than heavier. In a vacuum
all bodies fall equally fast. This may be illustrated by the Feather and
Guinea experiment, fig. 62, which is performed by a tall receiver h, contain-
ing several drop-stages ddd,on one of which is placed a gold-piece, and on
another a feather. The air being exhausted, these are allowed to begin
their descent at the same time, by allowing the stages to drop simultane-
8G
PNEUMATICS.
87
ously by the rod g, passing through the stuffing-box s. If the air is well
exhausted/ they will both reach the bottom at the
same time, showing that it is the resistance of the
air, which causes the feather and specifically lighter
bodies in general to fall slower than heavier ones.
126. The resistance on a sphere of 5 inches
diameter, falling through the air, has been esti-
mated to be 1.211 oz., when it acquires the velo-
city of 30 feet per second. But this resistance
is increased in a much greater ratio than the
velocity of the moving body, it being proportional
to the squares of the velocities (See under Stereo-
Dynamics). For this 'reason rain-drops, hail-
stones, and all kinds of projectiles, such as musket
and cannon balls, have all a maximum velocity in
the air, which they cannot exceed. But the larger
their size, or the greater the specific gravity of the
material of which they are made, the greater is
the velocity that can be given to them. Thus, a
bullet of lead is capable of a greater velocity than
one of iron. The flight of birds depends on this
same increase in the resistance of the air, the mo-
tion of their wings being performed, in one direc-
tion, both with greater surface and with greater velocity, than in the other.
127. Air which thus receives motion by impact or otherwise, will by
the same property of inertia continue its motion, on which the operations
of fanning and blowing depend, until it in its turn is checked by some
other cause ; for instance, by striking against other air, or against iru--
movable objects on the earth. The performance of windmills and the
sailing of ships depend on motion received by impact from moving masses
of air, which constitute winds. The power of winds increases in the same
augmented ratio of the squares of their velocities, which are stated to be as
follows :
Gentle breeze.
Pleasant breeze.
High wind.
Storm or gale.
Great storm.
Hurricane.
Vel. in
miles
per hour,
i. ... . 3.25
Vel. in
ft. per
second.
4.77
Inch, of
water
supported.
0.01
Pressure on
a square ft.
in Ibs. Avoir d.p.
0.83 oz.
ze. . . 6.5
9.53
0.04
3.33 "
. 16.25
23.83
0.25
1 Ib. 5 oz.
. . . 32.5
47.66
1.
5 " 3
. 56.29
82.56
3.
15 " 9 "
79.61
116.76
6.
31 " 3 "
mrricane. . . 97.5
143.00
9.
46 12 "
87
vy
128. The direction of the wind is generally ascertained by the vane,
but when feeble, by a suspended silk ribbon, or an ascending column of
smoke ; and sometimes also by the cold experienced on the finger, when
moistened and held up to the air. The force of winds is estimated by
instruments called Anemometers, the best of which are constructed on the
principle of the pressure-gauge (106) fig. 45, being made of large diame-
ter and containing water instead of mercury, having also the limb, acted
on, horizontal, so as to turn it against the wind. But those generally
adopted as the most convenient in meteorological observatories, are made
on the principle of spring-gauges, exposing a surface of a known area to
the action of the wind, the pressure on it being estimated by the compres-
sion of springs. Such has been made self-registering by Osier (L. & E.
Phil. Mag. vol. xi. p. 476), so that, being connected with a vane, it will note
by a pencil both the direction and the force of the wind for every moment.
* 129. When a gas is allowed to escape from a confining vessel through
a small or capillary orifice in a thin plate into a vacuum, the velocity with
which it issues remains the same ; for, as the density and consequent elas-
ticity or propelling force of the gas decreases, its specific gravity, and con-
sequently also the propelled quantity, decreases in the same ratio, so that
in the same time the same volume of gas always passes out, but of course
of constantly diminishing density.
If a gas be allowed to flow through a similar small orifice, but from a
vessel in which it is kept under a constant pressure (see gasometers ),
it will be found that the velocity with which it flows out increases rapidly,
as the space into which it flows is rendered more and more vacuous, until
the tension of the remaining air is only about Atm. (10 inches of mer-
cury), after which further exhaustion will not be found to increase the
velocity in the same proportion, and when the state of rarefaction reaches
gLth (1 inch of mercury, see 105), all further exhaustion seems scarcely
to affect the velocity, if the pressure on the gas be 1 Atmosphere. In this
manner, in 1000 seconds, 60 cub. inches (15148 fluid-grain measures) of
dry atmospheric air, have been found to flow into such a vacuum through
an orifice in a platinum foil of 3^0^ f an ^ ncn m diameter. The times
which the same volumes of different gases require for their passage into
such a vacuum, have been found to vary so as to be proportional to the
square roots of their specific gravities, and their velocities, therefore, under
the same circumstances, to be inversely proportional to these numbers.
Mixtures of gases ought to have a mean rate of their constituent gases ;
from which rule, however, some, as hydrogen and carburetted hydrogen,
have been found to make a remarkable exception, their rate being under
such circumstances diminished considerably beyond what it should be.
88
PNEUMATICS. 89
Thus, only 1 per cent, of air or of oxygen, added to hydrogen, was found
by Graham to retard its passage very perceptibly, and at least 3 times more
than it ought, by calculation.
130. If, however, instead of a capillary orifice in a thin plate, a capil-
lary tube of the same diameter be substituted, a very great change takes
place in the above rates, the velocities decreasing rapidly, as the orifice is
elongated into a tube, with the first additions, but becoming gradually less
affected, and after a certain length, they remain constant for any further
increase in the length of the tube. By a comparison of these ultimate
velocities for different gases, it is found that the ratios between them re-
main the same for a considerable range of pressures (from 1 to y^th Atm.),
but that these ratios are very different from those between their velocities
through capillary orifices. In some cases they approach to the ratios of
their different densities, but not uniformly so. Hydrogen and carburetted
hydrogen suffer also in this case, by admixture of other gases, a considerable
retardation over the mean of their mixture. And even for the same gas,
the velocity is found to change, becoming greater as the density of the gas
is increased, so that the higher the barometric pressure on it, in the less
time will the same volume of gas escape. Graham considers this a
proof that the effect cannot be ascribed to friction, and he therefore dis-
tinguishes the flow of gases into a vacuum through capillary tubes, from
their flow into the same through capillary orifices, designating the latter
by the name of E/usion, while their flow through capillary tubes he calls
Transpiration. When the space into which the gases escape, instead of
being kept vacuous, is allowed to become filled with the gas, the velocities
decrease slowly, while the tension of the gas increases from 1 to 10 inches,
r which, however, the decrease is very rapid (Graham's Chemistry, p. 86).
J.31. When gases issue under pressure into the Atmosphere, they seem
also to obey the same law that, for different gases, their relative velocities- "
under the same pressure are inversely as the square roots of their specific
gravities. For the same gas, its velocities under different pressures are as
the square roots of these pressures. Thus, according to Fyfe (Edinb.
New Phil. Journ., 1848, vol. xlv.), in 1 hour, 0.927 cub. foot of common
lighting gas (carburetted hydrogen), of spec. gr. 0.6026 (ref. to 60 as
stand.), will pass out through a jet formed of a circular orifice of -fa inch
in diam. under a pressure of j-JJ inch of water (burning with a flame 5
inch. high). Of a gas of 0.500 sp. gr., 1.118 cub. foot will pass out of
the same jet in the same time under a pressure of i-Jj inch of water.
\' 132. When a gas is allowed to escape under pressure from an orifice in
one side of a vessel, no pressure can of course be exercised by the gas
on this orifice, to counteract its corresponding pressure on an equal surface
89
90
BOYE'S INANIMATE MATTER.
Fig. 63.
on the opposite side of the vessel, hence this pressure must produce a ten-
dency in the vessel to move in the opposite direction of that in which the
gas flows out. This may be seen illustrated in the revolving gas-lights,
seen in shop-windows in cities. In these the gas is made to enter into
two lateral branches, see a and a fig. 63, which are capable of revolving,
their revolving motion being produced by the
gas escaping near the end on one side, while
no corresponding orifice or jet exists on the
opposite side, as seen in the horizontal section
at n and n . Instead of an orifice on the side
of the lateral branch near its end, the same
effect is produced by bending sideways the end
itself, this forming the jet.
133. If a thin plate of metal or pasteboard,
b fig. 64, be perforated at its middle, and fas-
tened by sealing-wax or otherwise at right
angles to the end of a glass tube a, so that the
aperture of the plate is directly over the bore of the tube, and another
card or piece of stiff paper c be laid over the opening, having a pin d
stuck through it, so as to prevent its sliding off, it will be impossible to
force it off by blowing through the tube. On the contrary, if the apparatus
be inverted, so that the paper is lowermost, blowing through the tube will
prevent it from falling down, and the greater the blast, the greater will be
the force by which it is held up. This experiment is called the Pneumatic
Paradox. The cause of this is, that as the air from the tube spreads out
when escaping between the plate and the paper, it can only separate them
to a certain distance (about ^ inch), since pushing them apart beyond
Fig. 64. Fig. 65. this, would cause its density to become less than
that of the atmospheric air on the other side of
the paper, and thus produce a partial vacuum
between them. That it is the atmospheric
pressure, which prevents the plate and the
paper from being separated, can be proved by
furnishing the other end of the tube with a screw
s } and attaching it to the air-pump plate, placing
over it a receiver with a stuffing-box and sliding
rod, by which the paper may be held up by a
loop fastened to it, till the air is exhausted, and
then let down on the plate. On readmitting
the air suddenly through the tube, the paper is blown off. Fig. 65
90
PNEUMATICS.
91
exhibits another modification of this experiment, the tube terminating in a
bowl c. By blowing through the tube g, a ball h of cork or any other light
material, will remain suspended, instead of falling or being blown out.
We will now give a separate consideration to the class of gases (45) f, \ .
whicfilfce called
134. Many liquids and solids, when their limit is towards a vacuum
towards a gas, are capable of passing wholly or in part into the gaseous
form, and of spreading in this state over the vacuum or through the gas.
Such liquids and solids are said to be volatile, while those which are not
capable of assuming the gaseous state (as oils), or owing to other circum-
stances, cannot be made to assume it (as platinum), are said to be fixed.
The gases thus formed are called vapors. This conversion into vapors
(vaporization) may take place either only from, the free surface, which limits
them towards the vacuum or the gas, in which case it is called Evaporation,
or if the substance be a liquid, the conversion into vapors may also take
place below the free surface, the vapors escaping as bubbles through the
liquid and agitating it, in which case it is called Ebullition or Boiling.
135. All vapors, being true gases, are, therefore, perfectly transparent;
and, when colorless, as invisible while vapors, as all other gases, until
they again assume the liquid or solid state, and at that moment again cease
to be vapors. It is, therefore, a popular error to apply the word steam,
by which we understand vapor of water, to the smoke or cloud formed by
the particles of liquid water, into which the steam again condenses at a
short distance from a steam-pipe, when escaping into the atmosphere.
Near the pipe, where it is yet real steam or vapor, it is as invisible as the
rest of the atmosphere. Even vapors of perfectly opaque bodies are trans-.,
parent and in many cases, such as that of mercury, also perfectly colorless.
In other cases, although always transparent, they may possess color. Thus,
vapor of sulphur is yellow, and vapor of Iodine is of a beautiful violet color.
Formations of vapors in a vacuum.
136. To illustrate the formation of vapors from volatile substances,
when limited towards a vacuum, we may employ a Torricellian Tube (60),
inverted in a large cup of mercury, see 1 fig. 66, and furnished with an
accurate scale to measure the height of the mercurial column. This
column, which is supported by the atmospheric pressure, we will sup-
pose to be exactly 30 inches. If we now introduce, through the mercury
in the cup d } the smallest possible quantity of water into the tube 1, it
91
92
BOYE'S INANIMATE MATTER.
will rise to the top of the mercury at 30, and thus present an upper or
free surface towards the Torricellian Vacuum. It^will then in a short
Fi 9 66 - time be found to disappear as
water, being converted into
vapor, the presence of which
as a gas in the vacuum is in-
dicated by its property of ex-
pansibility, that is, its spread-
ing over the vacuum with a
certain force, until it is resisted
by the limits of the latter, viz.
the sides of the tube and the
top of the mercury at 30,
thus causing a certain uniform
pressure on them all, called
its tension, and by which the
mercury becomes slightly de-
pressed below its former level
at 30. By introducing addi-
tional small quantities of
water, we shall find that the
same continues, the water dis-
appearing as liquid, and the
mercury becoming more depressed, until at last no more water is found to
disappear, and no more depression occurs, however much water we may
introduce, provided the temperature remains the same. Thus, if the
experiment be performed, when the stand of the mercury is 30 inches and
the temperature 59 Fah., this depression will stop at inch at 6, see tube
1 fig. 66, or when the mercury has a height of 29 J inches. If on the
contrary, the temperature be raised, more liquid will again disappear, more
vapor be formed, and the depression of the mercury become greater, till at
last, when it has reached a certain point, it again becomes stationary. If
the temperature be raised to 79, this will occur when the depression
becomes 1 inch, or when the height of the mercurial column is 29 inches, after
which the depression does not increase any further, as long as the tempe-
rature remains the same; and so on. We conclude from this, that the
formation of vapors from volatile liquids in a vacuum has a limit, which
depends on the temperature, so that for every temperature, there is a cer-
tain greatest or maximum quantity of vapor which can be taken up, with
a corresponding maximum tension, beyond which no more can be taken up.
92
PNEUMATICS.
137. An otherwise vacuous space may therefore, at a certain tempera-
ture, contain less than this maximum quantity, if there be no more liquid
present to form more vapor, but it can never contain more. The quantity
which is present, whether it be the maximum or less, is always, for the
same temperature, proportional to its tension, or the pressure which it
causes on the mercury. Should the temperature not be the same, a
deduction must first be made from its tension at the higher temperature
of so much, as is due to the expansion of the vapor by heat by the diffe-
rence in temperature (see 140 and 100). If, on the other hand, we can
prove, that a space contains the maximum quantity, or, as it is termed, is
filled to saturation with vapor, which may be known, for instance, by its
having been sufficiently long in contact with an abundance of the liquid,
then we may, from the temperature, estimate the quantity of vapor in the
space, and its tension, since these will be the maximum quantity and tension,
which correspond to the temperature.
138. By experiments, the following temperatures have been found to
correspond to the annexed maximum tensions and quantities of vapor of
water :
Temp.
Fahren.
Max. tens.
in
inch, of mercury.
Max. quan.
in 1 cub. foot,
in grains.
Temp.
Fahren.
Max. tens,
in Atmos.
Max quan.
in 1 cub. foot,
in grains.
149.65
i Atmos.
70.640
179.08
4 "
134.766
9KK '-t IT
250.52
2
ZuO.Oil
484.791
293.72
4 "
913.951
341.78
~X s*
8 "
1718.225 X^ 1 *
-^7^
le it will be seen, that at 212 the maximum tensio
of the vapor of water is equal to the atmospheric pressure, and that it-
therefore at that temp, will cause a depression of the mercury inside the
Torricellian tube to the same level as outside. The tension o'r elasticity
for higher temperatures than 212 cannot, therefore, be conveniently
estimated in the same apparatus as described above, but we may then sub-
stitute for it the apparatus represented in fig. 67, consisting of a small
boiler I I, furnished with a mercurial pressure-gauge c g, (106), the cistern
of which, c, communicates by an opening with the vapor inside the boiler,
so that by it we estimate the tension, while the temperature is indicated
by the thermometer t. The boiler is also furnished with a stop-cock i.
The boiler having been partly filled with water, the latter is made to boil
by the application of heat. As soon as the escaping steam has expelled
completely the atmospheric air, the stop-cock i is closed. The tension of
93
94
BOYE'S INANIMATE MATTER.
the vapor will then be found to increase rapidly, being indicated by the
Fi 9- 6r - height of the mercurial column in the gauge,
while the corresponding temperatures are in-
dicated by the thermometer. In the experi-
ments performed for the French Academy in
1829, by Arago and Dulong, for estimating
the elasticity of steam at higher temperatures,
the highest tension measured was 24 Atmo-
spheres. The tensions were estimated by a
condensed air-gauge (107), which had pre-
viously been tested by a mercurial gauge
(106) to the extent of 27 Atmospheres.
The tube of this latter was therefore over 68
feet high, having been ingeniously constructed
and arranged in an old church-tower. Mar-
iotte's law was thus found to be correct to
the above extent (Annal. de fhim. et de
Phys., 2d series, vol. xliii). The tensions
below 212 have been estimated with great
accuracy by Regnault (Ann. de Chim. et de
Phys., 3d ser., vols. xi, xiv and xv).
A complete set of tables of the tensions of
vapor of water in English inches, and the temps, in Fahr. degrees, has
been computed for this work from the tables furnished by these authors,
and will be found at the end of Pneumatics, JJT 1 TaMflfl VTT . VIII
is evident from these and the above-given table (138) of the
maximum tensions and quantities of vapor, that these increase with extra-
ordinary rapidity and in a much greater ratio than the temperatures, when
in contact with the liquid. This is due to the additional vapors formed
from it.* If, on the contrary, at any time, there be no liquid present, the
increase in tension will only be that which follows from the expansion of
the vapor by heat, which is the same as that of any other gas under the
* As regards the tensions of vapors at very high temperatures, it would seem from some
interesting experiments of Cagniard de la Tour, that they do not continue to increase in the
same augmented ratio. By enclosing volatile liquids in sealed glass tubes, and exposing
these to heat, he found that ether passed at 320 entirely into the state of vapor in a space
scarcely double its own volume, and without exerting a pressure of more than 38 Atmos.
Alcohol passed into the gaseous state at 404i, in a space of 3 times its own volume,
thereby exercising a pressure of only 139 Atmos., and water (to which a small quantity of
Carbonate of Soda had been added to prevent the breaking of the tube), in a space 4 times
its own volume, at about 648.
94
PNEUMATICS.
95
same circumstances, or for every degree Fahrenheit 0.00203611 of its
volume at 32, or 0.00217802 of its volume at 0.
141. Conversely, if vapors do not fill the space to saturation, as in the last-
mentioned case, when heated to a higher temperature without contact with
the liquid, or when allowed to spread through a vacuum in a less quantity
than to fill it to saturation at the existing temperature, such vapor may
again, without becoming liquid, be subjected to so much pressure or cold,
as will again reduce it to the state of saturation. But as soon as the pres-
sure becomes greater than its maximum tension at the existing temperature,
it will all be reconverted into liquid; and if the temperature becomes less
than that, at which its tension is the maximum, a portion of it will condense.
142. Thus, as an illustration of this in Tegard to pressure, suppose that
at the temperature of 79. 3 and 30 inches barometric stand, the Torricel-
lian vacuum b a c fig. 68 tube 1, contains vapor of only inch tension,
Fig 68. that is only the maximum
tension and quantity, which
belong to that temperature.
The level of the mercury will
then of course be at 29
inches, or at b. The vapor
being thus only J the quantity
that can exist in the space, it
may be subjected to an addi-
tional pressure of J inch, or
till its volume is compressed
to $ of its former volume, or
into c a, without any conden-
sation taking place. This in-
crease in pressure is produced
by inclining the tube, as tube 2
in the fig., which has the
effect of diminishing the Tor-
ricellian vacuum above the
mercury, by which the vapor
becomes more compressed, and
its density and tension thereby greater, so that it depresses the mercury
more, say to 29 1 inch at b t . The compression of the vapor may thus be in-
creased by still farther inclining the tube, without any condensation occur-
ring, until the depression in the perpendicular height of the mercury is 1
inch, or the perpendicular height of the mercurial column 29 inches, see
95
96 BOYE'S INANIMATE MATTER.
tube 3, when, in consequence, the atmospheric pressure on the vapor will be
30 29 inches, = 1 inch of mercury. At the same time the vapor will
also be compressed to the volume c a a a , that is J its former volume, and its
tension in consequence doubled or equal to 1 inch. The pressure on the
vapor being thus equal to its maximum tension at that temperature, any
farther inclination of the tube will not cause the mercury to become more
depressed, but merely diminish the Torricellian space, by which as the
space become diminished, the vapor in it will be compressed to liquid water,
till at last, when the top of the tube reaches the level of 29 inches, see tube
4, no vapor will remain, all having been converted into^ liquid, which will
appear as adrop at the very top of the tube.-~""*"**- : p >5 i^2xV/\
"*T43. In tn"e same manner, as regards temperature, if the tube" or any
other vessel containing vapor, not filling it to saturation, be subjected to
cold, the temperature may be lowered without any condensation taking
place, until it reaches that degree at which the vapor forms a maximum,
after which a portion of it will be reconverted into liquid, only leaving so
much vapor, as will be the maximum at the temperature to which it is
cooled. Thus, as in the above case, if the temperature be 79. 3, and the
tube contain vapors of only J inch tension, which is only J the maximum
tension and quantity corresponding to this temperature, it may be cooled
without any condensation taking place, to the temperature of 59, this
being the temperature at which its tension will be the maximum. But if
then the temperature be still farther lowered to 40, so much of it will
condense, that what remains has only a tension of \ inch, which is the
maximum at that temperature. As the condensation of a portion of the
vapor gives the appearance of a dew on the sides of the vessel, the tempe-
rature at which this begins to take place, is called the Dew Point. The
condensation of a portion of the vapor or its appearance as a dew, by the
slightest increase in cold or pressure, is the surest proof that the space is
filled with vapor to a maximum or to saturation.
144. The formation of vapors by boiling, will take place whenever the
temperature of the liquid becomes so high, that the maximum tension,
which corresponds to its temperature, is equal to, or greater than, the ten-
sion or pressure of the vapor on its free surface. By this the liquid
will be capable of forming vapors below the free surface, which vapors
generally appear as small bubbles on the surface of the containing
vessel, where the liquid *is in contact with it, and which bubbles force
their way through the liquid, and agitate it. In a close vessel, like
that of fig. 67, the temperature of the water may, therefore, by a very
gradual heating be raised, without producing boiling, to any degree, the
maximum tension of which the vessel will bear without bursting, since
96
PNEUMATICS.
97
by such gradual heating the formation of vapor by evaporation from the
free surface, will keep pace with the maximum tension, which corresponds
to the temperature of the liquid. If, however, the vessel be heated very
suddenly from below, so as to raise the temperature very rapidly, boiling
may be produced for a short time, till the tension of the vapor above
becomes the maximum for the temperature of the liquid. Another much
easier way of producing boiling on the same principle, is by suddenly
diminishing the tension of the vapor on the free surface. This may be
done, where the tension is greater than the atmospheric pressure, as in the
apparatus^. 67, by letting the vapors escape into the air by opening the
stop-cock ij by which a violent ebullition will take place, until the temp,
of the liquid is again lowered to 212, which is the temperature which cor-
responds to the diminished pressure of the vapor on its surface (1 Atm).
145. Another mode of diminishing the tension of the vapors, particularly
if less than the atmospheric pressure, is by their condensation, absorption,
or exhaustion. Thus, the production of boiling by condensation of the
vapors, by applying cold to that portion of the vessel where they are con-
Fig. 69. tained, may be illustrated by an experiment, known
under the name of the Culinary Paradox (so called
because it produces boiling by cold), which consists in
boiling water in a globular glass vessel with a long
neck (bolt-head), till all the atmospheric air is expelled.
It is then quickly closed up by a cork, while removing
it from the fire, and inverted as in fig. 69. By apply-
ing carefully, so as to prevent its breaking, a piece of
ice or a sponge moistened with cold water to the top at
c, where the vapors are contained, these are condensed,
and the water will then begin to boil violently.
146. Strong vessels for heating liquids to a high
temperature, furnished with a safety-valve to regulate
the highest temperature of the liquid, and consequent
pressure of the vapor, affording the latter an escape, if exceeding a certain
Fig. 70. limit, are known under the name of Papin's Digestor, see
fig. 70. Such have been applied to different purposes by
the greater solvent power, acquired by liquids at tempera-
tures higher than their boiling point in open air; for
instance for the extraction of gelatine from bones by water,
or the solution of resinous substances for varnishes by alco-
hol or oil of turpentine.
147. From the table given in 138 it will be seen, that
G 97 9
98 BOYE'S INANIMATE MATTER.
water continues to emit vapors many degrees below its freezing point, and
that, therefore, even ice is volatile. The question therefore arises : do
volatile substances continue to emit vapors at all temperatures, however
low, although of course in a continually diminishing ratio, so that for those
substances which are volatile to a perceptible degree only at higher tem-
peratures, their evaporation becomes at last inappreciable, and, therefore,
imperceptible at lower temperatures ? or do they exhibit at a certain tem-
perature a theoretical or absolute stop to the further formation of vapors ?
According to the experiments of Faraday, mercury has been found to
begin to emit a very small but perceptible quantity of vapor in summer
between 60 and 80; but in winter the formation of not even a trace
could be detected by the most delicate tests. It seems therefore probable,
that volatile substances cease all at once to emit vapors, and that this point
will be arrived at, when their expansive or evaporative power becomes
so small, that it is counteracted or overcome by the forces of cohesion and
^gravity (compare also 27).
* i4#T The maximum quantities and corresponding maximum tensions
of other volatile substances for the same temperatures, are different from
those of water, being greater for the same temperature, the more volatile they
are. An idea of their relative volatility may be obtained by referring to
their boiling-point in air (see 154), which indicates the temperature at which
their maximum tension is the same as that of water at 212. The lower
their boiling point, of course the greater is their volatility. But the ratio
of the increase of the tension of their vapor, to the increase in the tempera-
ture, is somewhat different for the different substances. Thus the boiling-
point of mercury is 662, and the tension of its vapor at that temperature,
therefore, 30 inches, or 1 Atm. For lower temperatures Regnault obtained
the following maximum tensions of its vapor in a vacuum :
Temperature 212.2 144.93 120.47 77.7
Tension 0.160 in. 0.0072 in. 0.0034 in. 0.0013 in.
149. It will be evident from the foregoing, that the conversion of vola-
tile substances into vapors in a vacuum is facilitated : 1st, by an increase
in the temperature, and, 2d, by the removal of the vapor as fast as it
is formed. The latter may be effected either by condensation, by the
external application of cold to a different part of the vacuum at a distance
from the liquid; by absorption, by placing in a different part of the
vacuum a substance, that by its adhesion or chemical affinity will attract
and thereby remove the vapors ; or in some cases by exhaustion of the
vapor by an air-pump.
150. In the same manner as the removal of the atmospheric pressure
98
PNEUMATICS.
99
will cause the expansibility of gases to overcome their adhesion to solids
(121) or liquids (120), so the placing of volatile liquids in a vacuum will
have the same effect, causing their expansive or evaporative power to over-
come their adhesion or even feeble chemical affinities. Hence in chemistry,
desiccation or drying, evaporation and boiling, and the expulsion of che-
mically combined water, are often effected or assisted by placing such sub-
stances with suitable arrangements in a vacuum.
^ ^
S\
rmation of vapors in a
151. To illustrate the formation of vapors from liquids, when their
limit is towards a gas, we may use several receivers, see d and Ti
fig. 71, filled with different gases, such as atmospheric air and hydrogen,
Fig. 71. and placed in a pneumatic cistern . . . . ,662
.
155. If, however, the atmospheric pressure on the surface of the water
or other volatile liquids be increased, it will require a higher temperature
to produce boiling ; and if it, on the contrary, be decreased, boiling will
take place at a lower temperature. If, therefore, water of less tempera-
ture than 212, or even of ordinary high temperatures (70 to 80) be
placed under a receiver, and the air quickly exhausted, it will begin to boil.
156. As water emits vapors of a certain tension at all temperatures, it
might be supposed that by removing all pressure from its surface, it could
be made to boil at any temperature. This is, however, not the case, as it
cannot be made to boil, even in a perfect vacuum, below the temperature
of 67. The reason of this is, that although at this temperature it is yet
capable of furnishing vapor of a tension of more than J inch of mercury,
this tension is not sufficient to overcome the pressure caused by the weight
of the layer of liquid above it, or to break the cohesion of its particles.
Other volatile liquids have a similar limit or lowest temperature, below
which they cannot be made to boil in a vacuum, being approximately the
same number, or 145 below their boiling-point in open air.
157. The principle, that the temperature at which . pure water boils
depends on, and varies with the atmospheric pressure, being always that
at which the maximum tension of its vapor is equal to the atmospheric
pressure on its surface, is used in the construction of the Boiling-Point
Barometer, described in 87.
158. From the foregoing it will be evident, that the conversion of vola-
tile liquids into vapors in a gas in a close vessel, or in the open atmo-
spheric air, is facilitated : 1st, by heat, and, 2d, by the removal of the
vapor as fast as it is formed. This latter may be effected by condensation,
by applying externally cold to another part of the close vessel at a distance
from the liquid (Distillation) ; by absorption, by placing in a different part
of the close vessel substances, which, by their adhesion or chemical affinity,
will attract and thus remove the vapor ; or by displacement of the satu-
101
102 BOYE'S INANIMATE MATTER.
rated air over the liquid by less saturated or perfectly dry, and, in some
cases, even heated air.
159. These principles are often applied in chemistry for effecting or
accelerating the drying of vessels or substances containing water. Thus,
the drying of narrow-mouthed vessels, such as bottles, which even by heat-
ing requires considerable time, is effected in a few moments by removing
the saturated air by suction through a tube, the other end of which is intro-
duced to the bottom of the vessel.
Vapor of Water in the Atmosphere.
160. The atmosphere always contains Yapors of Water (26), which are
formed by evaporation from the sea and the moist earth. From various
causes (92), these again condense to liquid water either on the surface of
the earth as dew, or in the atmosphere itself as small hollow spheres or
vesicles, filled with air, which constitute fogs and clouds.
These vesicles may be observed by a lens of 1 inch, focus against a dark ground. Saus-
sure found those forming the mist on high mountains to have a diameter of 45^17 to v-J-g-Q
inch, but occasionally to be as large as a pea. A fog is a cloud resting on the earth. On
the other hand, by ascending into the clouds, these appear as fogs. According to Howard
the different varieties of clouds are named as follows :
Cirrus, Curl- or Feather-Cloud, composed of delicate feathery streaks or filaments, more
or less straight, curly, or confused. After a spell of fine weather they are generally the
first to change the blue color of the sky, and they are often the last remaining, when the
weather becomes fine. They are the highest of all clouds, and have, in some cases, been
estimated to have an elevation of 20,000 feet.
Cumulus, Accumulated or Heap-Cloud, forming large hemispherical masses, with a more
or less horizontal base. They are often piled on each other, and when lighted by the sun,
appear as mountains of snow. In hot weather they frequently appear as the heat of the
day increases, and disappear again toward evening.
Cirro-Cumulus, is the name given to those small, white, generally rounded clouds,
arranged in rows, mostly with the blue sky visible between them. After rainy weather,
the clouds often break into these, and they give to the sky a mottled appearance (Mackerel-
back sky).
Stratus, Layer-Cloud, forms a misty layer of clouds near the earth. It often forms at
sunset, and again disappears after sunrise. It sometimes resolves itself into a heavy dew,
at other times it rises as cumulus.
Cirro-Stratus, forms streaks or bands, but heavier than the cirrus, which often passes
into it. When in the horizon it causes the beautiful colors of the sunset; but when heavy
gives it the dark-red appearance, which by many is considered as the precursor of rain.
When high up, it often appears as attenuated clouds, covering the sky as with a veil, but
at other times it assumes a darker and more threatening aspect.
Cumulo-Stratus, consists of dense masses and layers. It is generally formed by the
increase of the cumulus, extending irregularly at the top, and losing its straight base by
the addition of irregular appendages hanging down from it. It is then apt to pass into
the next.
Nimbus, or real rain-cloud, characterized by its uniform grey or dark appearance, with
102
PNEUMATICS. 103
fringed or indistinct edges, not allowing the different clouds of which it is composed to be
well distinguished.
The word Scud, is often applied to the loose and low masses of clouds, which during a
storm are seen to move with great rapidity below the other clouds, and often in a different
direction from them.
When the vesicles of the clouds break and unite into solid drops, they form rain. As,
in the rule, the atmosphere near the earth must always become saturated with vapors,
before rain can fall, the rain-drops increase in their descent by the condensation of addi-
tional vapors on their surface, and their size therefore depends on the height of the clouds.
This increase is very perceptible by measuring the quantity of rain falling at different
heights in the same place. Thus, an increase in the annual amount of rain of over one-half,
has been observed in a fall of 240 feet. The amount of rain which falls is estimated in
inches, indicating the depth of the layer of water which it would form, if allowed to
remain standing on the earth. The instrument used for this purpose is called the Rain-
gauge or Ombrometer, and consists of a funnel, the mouth of which has a known area, and
which discharges the water into a large bottle or other suitable vessel of sufficient capacity,
in or from which it is measured in cubic inches. The number of cubic inches, divided by
the number of square inches constituting the area of the mouth of the funnel, gives the
height or depth of the water fallen. Thus, if the mouth of the gauge be circular
and 7.98 inch, in diameter, each cubic inch of water will correspond to 0.02 inch of rain.
Rain-gauges may also be made self-registering (Osier's). The annual amount of rain
increases from higher latitudes toward the equator, varying from 13 to 126 inches. In
Philadelphia (Penn. Hospital) it is 44 inches. But the number of rainy days, over which
the fall of the rain is distributed, varies in the reverse order.
Hailstones are frozen rain-drops, their size increasing by a prolonged suspension in the
atmosphere by powerful upward currents or by electricity. Snow is formed by the freezing
of vapor or of the vesicles. Snow-flakes often exhibit the most beautiful starlike appear-
ances, varying much in the form of their rays, but are always of the same form in the same
snow-fall. Their' form is produced by the different small crystals of which the flake is
composed, arranging themselves in different manners, although always at the same angles.
161. The two most important forms in which water exists in the atmo-
sphere, are, therefore, in the liquid state as vesicles, and in the gaseous
state as vapor. Both states constitute what is commonly (see 162) under-
stood by the dampness or moisture of the atmosphere. When, however,
the atmosphere is perfectly transparent, the water may be considered as-
existing entirely in the state of vapor. But even in this state, when
approaching the point of saturation, it imparts to the atmosphere ? .f 1 '^ided
dampness; and by depressing the perspiration of the skin, which cannot
pass off as vapor, when the air is saturated, it causes such air, if cold, to
feel chilly and harsh or raw, and, when hot, sultry and oppressive. In the
same degree also, as the air approaches the state of saturation, the tendency
of the vapor to precipitate in the liquid state, increases, and it therefore
becomes important to estimate at any time the vapor in the atmosphere,
ind its approach to saturatio
or humidity, or absolute moisture or humidity,
in the meteorological sense, is understood the quantity of water, which
exists in the atmosphere in the state of vapor, while by relative mois-
103
104
BOYE'S INANIMATE MATTER.
Fig. 72.
ture or humidity, is understood the fraction which this constitutes of the
maximum quantity or of saturation for the existing temperature. Thus,
a relative humidity of 0.31 means, that the atmosphere contains y^ths of
the quantity of vapor, which at the temperature in question, whatever this
may be, would constitute saturation. Instead of referring the relative
humidity to saturation as 1, it is often referred to it as 100, in which case
the above relative humidity will be 31. It is therefore on the relative
moisture, and not on the absolute quantity of vapor, that what is commonly
called the dryness of the air depends, for if the quantity of vapor only
forms a small portion of the quantity which constitutes saturation, the air
will yet freely take up more vapor, and therefore appear dry. Thus the
same air that in winter is called damp, will in summer, when the tempera-
ture is higher, appear dry.
163. The most accurate way of esti-
mating the quantity of vapor in the atmo-
sphere is by the chemical method, see fig.
72, which consists in passing a known
volume of air though a U-shaped tube e,
filled with pieces of pumice-stone, pre-
viously moistened with oil of vitriol,
which absorbs all the vapor from it. The
air is drawn very gradually through this
tube by connecting it with the aspirator g
filled with water, which latter is allowed to
run out very slowly through the stop-cock
, and thereby draws the air through the
tube e } to replace it. The tube c is also
filled with pumice, moistened with oil of
vitriol, but is permanently attached to
the aspirator, to prevent any vapor passing from it into the tube c. The
tube d is similarly filled, but serves only as a check to ascertain whether
all the vapor has been absorbed by the tube e, and may be dispensed
with. The tube e is weighed accurately before and after the experiment,
and its increase in weight is the amount of vapor in the volume of air
drawn through it by the aspirator #. This volume is estimated by measuring
the quantity of water which it holds. A strict account must be kept of
the temperature of the air during the experiment, by placing a thermometer
at /, where it enters the tube. The aspirator is also furnished with a
thermometer b u } and should its temperature at the end of the experiment
differ from the average temperature of the air which entered, its volume
104
PNEUMATICS. 105
must be reduced to the same, making also a deduction for the quantity of
vapor in it, and for any variation in the barometric pressure during the
experiment (100). Should the state of moisture of the room in which the
experiment is performed be different from that of the atmosphere, the air
must be drawn in from the outside by a longer tube. Having thus
obtained by weight the absolute quantity of vapor in a certain volume of
the atmosphere, the relative humidity is easily obtained by dividing this
obtained quantity by the maximum quantity for the same volume (168),
corresponding to the observed temperature of the air; or the tension of the
vapor may be calculated from the obtained weight (168) and divided by
the maximum tension for the temperature of the air (164). This method
allows us also to estimate the quantity of vesicular water existing in the
atmosphere, since in such case the air must be saturated with vapor, and
its quantity, therefore, equal to the difference between the quantity
obtained by the experiment, and the maximum quantity for the tern]
ture. It has, however, the inconvenience, that it requires longerTime,
considerable skill in the operator, and expensive apparatus, particularly K
for weighing the tube with sufficient accuracy. Other methods and instru- V
ments have therefore been contrived, which will now be described.^
HYGROMETERS.
164. By hygrometers (from hypos (hugros) moist, and fjLsrpov (metroii),
measure), we understand instruments for estimating the moisture of the
atmosphere. The best of these act on the principle of finding the Dew-
Point, that is, the temperature at which the vapor existing in the atmo-
sphere would be the maximum quantity or fill it to saturation. This is
done by cooling a portion of it till the vapors condense as a dew (143),
and then observing the exact temperature at which this begins to take
place, which temperature constitutes the dew-point. As the vapor in the
atmosphere is not confined, but free to contract or expand, the maximum
tension corresponding to its dew-point must be the same as its tension in
the atmosphere at the existing temperature, and will therefore bear the same
ratio to the maximum tension corresponding to the temperature of the
atmosphere, as its quantity bears to the maximum quantity for this same
temperature. We therefore obtain the relative humidity of the atmosphere
~by dividing the maximum tension, corresponding to the temperature of the
Dew-Pointy by the maximum tension corresponding to the temperature of
the atmosphere. For this purpose the maximum tension for every 0.2 degree
Fah. from 104 to will be found in Table IX, at the end of Pneum.
Thus, suppose that the
Dew-Point == 60 Temp, of Aim. = 85 ;
105
106 BOYE'S INANIMATE MATTER.
we then have from Table IX,
Max. Tension for 60 = 0.518 inch
" " " 85 = 1.203
therefore : Relative Humidity = - 518 = 0.431 ;
that is, the atmosphere contains y^^ths of the quantity of vapor, which it
is capable of taking up, and which would constitute saturation at its tem-
perature of 85. Instead of referring to saturation as 1, the relative
humidity is often referred to it as 100. In the above case it would then
be 43.1.
165. Conversely to find from the relative humidity and the temp, of the
atinos., the tension of the vapor in it and the dew-point, we multiply the
max. tens, for the temp, of the atmos., taken from Table IX, by the rel.
humidity referred to saturation as 1, which gives us the tension of the vapor
in the atmos., and as this is also the max. tension for the dew-point, the
temp, which in Table IX corresponds to this tension is the dew-point, f
166. To obtain the quantity of vapor in the atmosphere, either ly
volume or l>y weight, referring it to the atmospheric air itself as 1 (which
if referred to it as 100, constitutes the per centage by volume or by weight),
we may consider vapor of water as obeying Mariotte's law, both as regards
its volume and its density in the atmosphere. To estimate, therefore, its
volume, it must be kept in mind, that while occupying the whole volume
of the atmosphere through which it is diffused (the observed volume), it
only sustains so much of the atmospheric pressure as is equal to its own
tension /, and that to obtain the true volume V, which it would occupy
under the whole atmospheric pressure B (see 100), we have that :
F: Vol. of Atmos. ::1 :1
f
therefore, calling the volume of the atmosphere 1, we have
/ being = the tension of the vapor, which is the same as the maximum
tension for the dew-point, and B = the stand of the Bar. Thus, suppose
the dew-point = 60, and the stand of the Bar. = 29 inch., we then have
from Table IX, that the max. tension for 60 = 0.518 inch, and therefore :
V = ^15.= 0.01786;
29
that is, the volume of the vapor constitutes 0.01786 of that of the atmo-
sphere, or it is 1.786 per cent, by volume.
167. To obtain the weight of the vapor in the atmosphere, referred to
that of the atmosphere itself as 1, we multiply the tension of the vapor by
0.622 (Sp. grav. of Yap. Water), and divide this product by itself after
106
PNEUMATICS. 107
having added to it the difference between the stand of the Barometer and
the tension of the vapor. Or, calling the weight of the vapor W } we have :
0.622 /
= (Bf) -f 0.622 /
/ being = the tension of the vapor, which is the same as the maximum
tension for the dew-point, and B = the stand of the Barometer. Thus,
suppose, as in the former case, the stand of the Barometer = 29 inch, and
the dew-point 60, we then have as before, from Table IX, the maximum
tension for 60 = 0.518, therefore:
W ' 622 * 0-518 =0.01119;
(29 0.518) + 0.622 X 0.518
that is, the weight of the vapor is 0.01119 of that of the atmosphere, or it
is 1.119 per cent, by weight.
168. To obtain the absolute weight of the vapor in a given volume , for
instance, in 1 cubic foot of the atmosphere, or what is the same, since this
quantity is the same as if the space contained no air, the absolute weight
of 1 cubic foot of Vapor of Water, we have by Mariotte's law, as stated
in 166, that the densities of the vapor in the air at ordinary temperatures
may be considered proportional to the pressures on it, the pressure on it
at any time being the same as its tension. We know also that its expan-
sion by heat is the same as that of other gases (140). To find, therefore,
the weight of vapor in 1 cubic foot of the atmosphere, or 1 cubic foot of
vapor of the tension and temperature in which it exists in the atmosphere,
we proceed as directed in 100, by first reducing 1 cubic foot (considering
this as the observed volume of vapor) to the standard pressure (29.918
inch.) and temperature (32), and then multiply the thus-reduced volume,
first, by the weight of 1 cubic foot of atmospheric air of the same standard
pressure and temperature (= 563.1007 grains), and then by the specific
gravity of Vapor of Water (= 0.622), so that calling the weight of the
vapor in 1 cubic foot W, we have :
W = 1 X 297918 X 1+0.0020861 (<-32) X 563 - 1007 ^ X ' 622
= 11.7055 grs. X 1 + 0.0020361 ($82)'
f being = the tension of the vapor, which is the same as the maximum
tension for the dew-point, and t = the temperature of the atmosphere, or
of the vapor. Thus, suppose the dew-point = 60, and the temperature
= 85, we then have from Table IX the maximum tension for 60 = 0.518
in., and therefore the weight of vapor in 1 cubic foot, W:
0.518
(F= 11.70660". X 1+00620861 (85 Q -32)
= 5.473 grains,
107
108
BOYE'S INANIMATE MATTER.
By actual experiments, Regnault found that the quantities thus calculated
on the above-stated supposition, that vapor of water, when diffused through
air, obeys Mariotte's law, and that its tensions and densities are the same
as in the vacuum, were only about 1 per cent, greater than those obtained
by actual weighing of the vapor (compare 152).
Hygrometers giving the Dew-Point.
169. DanieWs Hygrometer. It consists of a mode-
rately wide glass tube, see ah fig. 73, blown out at its
two, extremities into bulbs, and bent twice at right
angles. One bulb is partly filled with liquid ether,
while the rest of the apparatus is freed from atmo-
spheric air, but contains, of course, vapor of ether.
The bulb d containing the ether, has a thermometer
inside ; while the other bulb c is covered with thin
muslin. To use it, we first pour ether, drop by drop,
on the bulb c, which ether, by its evaporation, pro-
duces cold (see Latent Heat under Thermics), and thereby condenses the
vapor inside. By this, the tension or pressure of the vapor on the liquid
ether in the other bulb d is removed, and the ether in it thereby
begins to boil, or evaporate very rapidly (145). The temperature of the
remaining ether in the bulb is thus lowered, and thereby that of the bulb
itself and the atmosphere surrounding the bulb on the outside ; till at last
the vapor of the atmos. forms a maximum, and then begins to condense on
the outside of the bulb as a dew. At this moment the temperature of the
bulb is observed by the thermometer inside, and this gives the temperature
of the dew-point of the atmosphere. As this is apt to have been observed
too low, the thermometer should also be read off, when the dew again dis-
appears, and the average between the two observations, taken, as the true
dew-point. Generally, the stand g on which this instrument is supported,
is furnished with a thermometer, by which the temperature of the atmo-
sphere at the same time, is ascertained.
Daniell was the first to furnish us with a practical hygrometer on a true
scientific principle that of finding the dew-point. It has, however, this
inconvenience, that, as the cooling of the ether takes place from the upper
surface and is not readily communicated to the layers below, the thermo-
meter is apt not to indicate accurately the temperature at which the dew
deposits. When the dew-point is very low, it is also difficult to manage,
and if not observed at the moment when the first dew appears, which may
easily escape notice, it gives the dew-point too low, and the experiment
must be repeated. To facilitate the observation of the first dew, the bulb
108
PNEUMATICS.
109
made of dark glass, or it is furnished with a gilt band or zone
nd it. " ^ *- ^ $MjZs^-^^
170. J9acAe's Hygrometer, see ^. 74, consists of a horizontal bar or
Fig. 74. tube a c, of steel or brass, kept bright on the
outside, the one end of which is inserted in a
box Z>, containing ice, or ice and salt, by which
its temperature is made to decrease gradually
from the free end a, which has the tempera-
ture of the atmosphere, to the end c inserted
in the box. At the point, which has the temperature of the dew-point of
the atmosphere, the moisture will begin to precipitate and form a very dis-
tinct limit, from which its amount increases more and more toward the
cooled end. To ascertain accurately the temperature of the bar, where
the moisture begins to precipitate, and which indicates the dew-point, that
portion of it which is outside the box is hollow, being varnished inside, if
of brass, and filled with mercury, in which the bulb of a small delicate
thermometer t slides, the stem of which passes through a longitudinal
Fig. 75. Fig. 76. opening on the upper side of the bar as
seen in the figure. This thermometer is
moved to the exact place, where the mois-
ture begins to condense, and its tempera-
ture then indicates the dew-point. For
stationary observatories, where ice is easily
had, this hygrometer is very convenient,
being easily observed.
171. Regnault's Hygrometer (Jiygro-
metre condenseur) is a modification of
Daniell' s, but so contrived as to be easily ..
managed and to give results of the utmost
accuracy. Fig. 75 represents it in sec-
tion. It consists of a glass tube h of
0.8 inch, diameter, having on the side near
the top a small horizontal tubulure t. Its A
lower end is closed by being inserted into
an extremely thin and highly polished
silver cup or thimble b of the same diame- fJ -,'i
ter, and about If inch, high, but with a
round bottom. This and portion of the
glass tube up to m is filled with ether, or, as a substitute, with alcohol. The
upper end of the instrument is closed by a cork a, through which is
109 10
110
BOYE'S INANIMATE MATTER.
inserted a narrow open glass tube g, reaching nearly to the bottom of the
silver cup, and a very accurate thermometer p, the bulb of which is in the
middle of the ether.
The horizontal tube t is connected with an aspirator similar to g, fig. 72,
but of smaller size, by which air may be drawn with any desired rapidity
through the tube g } so as to bubble through the ether. By this contrivance,
the evaporation of the ether is under perfect control. When the cooling
which it causes reaches the dew-point, the vapors of the atmosphere appear
on the outside of the silver cup, and the thermometer is observed. The
aspiration is then stopped, and the dew allowed to disappear, and the
temperature when this happens, again observed. The true dew-point will
then be the mean between these two temperatures. Should it be desired
to estimate it with more accuracy, the aspiration is immediately started
again, but much slower, and the same experiments repeated. By this con-
trivance the dew-point may be estimated to -J^ of a degree. To be better
able to observe the slightest dew by comparison with another similar appa-
ratus, Regnault fixes two such together by the tube c d, which connects
them both with the aspirator, as shown in jig. 76, but the second of which,
h is not used at the same time, and therefore contains no ether, and has
the tube g closed up. The thermometer of this maybe used for indicating
the temperature of the atmosphere.
August's Psychrometer (from
1130 T l
in which T== the temperature of the atmosphere in Fah. degrees given by
the dry thermometer; ^^the temperature in Fah. degrees of the wet-
bulb thermometer; JF = the maximum tension in English inches for the
temperature T of the wet-bulb thermometer, and which is found in Table
IX; and J5 the stand of the Barometer in English inches.
If the observations are taken below 32, when the wet-bulb therefore is
covered with ice, we must substitute in the above formula, instead of
1130 T t which represents the latent heat of the vapor, 1272.2 T the
formula then becoming :
0.480 (r-TM
1272.2 T'
Having thus obtained the tension of the vapor in the atmosphere, the
relative humidity is easily calculated (164) by dividing this tension by the
maximum tension for the temperature T of the atmosphere, given by the
dry thermometer, and which tension is found in Table IX. If the dew-
point be required, it is easily obtained by taking from Table IX the tempe-
rature which corresponds to the tension /, obtained by the above formula,
111
112 BOYE'S INANIMATE MATTER.
174. To illustrate this by an example, suppose that the
Dry Therm. = 68 = T Wet Bulb Therm, = 59 = T l
Barom. = 29.922 inch. = B
We then have ;
T T } = 9
and from Table IX, F^ = 0.500 inch.
Therefore, by the first formula :
0.480x9
/=0.500 1130 __ 59 X 29. 922=0.379 inch;
which is therefore the tension of the vapor in the Atmosphere; and 513
which in Table IX corresponds to this tension, is the Dew-Point. From
Table IX we then obtain :
Max. Tension for 68 = 0.685 inch.
Therefore :
Relative Humidity = - r .0.553;
or = 55.3, if referred to saturation as 100.
To avoid these calculations, Tables have been constructed, which give
from the temperature T^ of the wet-bulb thermometer, and the temperature
T of the atmosphere or the difference T T between the dry and wet-
bulb thermometers, both the tension of the vapor in the atmosphere, and
the relative humidity, which at the temperature T of the atmosphere cor-
responds to this tension, supposing the Barometer to remain at the same ave-
rage stand. If it should be required to make a correction for the different
stands of the barometer, a table may also be constructed for this purpose.
[The formula given by August, of Berlin, the inventor of this instrument, and which
0.568 (t t')
is yet used extensively, is : = /' 64Q _ - h; in which x = the tension of vapor
in atmosphere in millimetres ; t and t' = temperatures of dry and wet bulb thermometers
in centigrade degrees ; f = maximum tension of vapors at temperature if, in millimetres ;
and h = stand of Barometer also in millimetres. By correction of some of the numerical
0.429 (t t' )
data, Regnault has since altered this into: x =/' -- glO^T' ^ which he found to
give correct results, whenever the relative humidity is less than 0.40 (which results differ
not much from those obtained by August's formula, using August's Table of Maximum
Tensions, but when taken for a wider range are not so near the truth). But whenever the
relative humidity is over 0.40, Regnault has found, that in order to obtain perfectly correct
results, it is necessary to substitute the coefficient 0.480 for 0.429, the formula then becoming:
h, and for temp, below the freezing point :*=/' '~ h,
which are the formulae given above, only with the proper substitutions for using English
inches and Fahr. degrees. With the same substitutions August's formula becomes:
0.568(72;) 0.429(77;)
f=Fi 1184: _y B > and as corrected by Regnault: /= Ft 11;j0 _ y> - ]
112
c/a
PNEUMATICS. 113
175. For low temperatures this instrument gives less accurate results,
on account of the small differences between the temperatures of the
dry and wet-bulb thermometers ; and when the temperature of the atmo-
sphere is near the freezing point, its results are very unsatisfactory, on
account of the uncertainty in the freezing of the water. Regnault also
found that in order to obtain good results, a free change of air is abso-
lutely necessary, so that in a close room its indications are less correct,
the wet-bulb thermometer not descending to its proper point, and therefore
giving the relative humidity too high. For observations, it is therefore
generally placed in an open window, or fixed permanently outside of it.
But even when thus placed, the air, if very still, should be agitated about
the bulb by fanning. On the other hand, too strong currents of air will
affect the results in the opposite direction, so that if the existing wind
have a greater velocity than from 15 to 18 feet per second, the instrument
should be screened from it. Otherwise, Regnault found that within the
ordinary limits given to this instrument, it is not influenced perceptibly
by the size or shape of the thermometer-bulb, nor by the thickness of the
covering muslin, nor by the manner of moistening it either by immersion
of the bulb, or by supplying it by a wick from a small vessel ; nor in the
latter case, by the length of the wick, or the quantity of water by which
it is moistened, provided this be sufficient for complete moistening and
full evaporation, so that if supplied from the wick in larger quantity than
this, it may even without injury cause a drop to fall occasionally from the
bulb, but in no case should it exceed this quantity. The water used for
moistening, should be pure, as otherwise by its evaporation it causes
too great a deposit of earthy ingredients on the bulb. Rain-water is,
therefore, preferable. To remove impurities which collect on the bulb,
it should be cleaned, and the covering renewed at least every two or three
months.
176. The Psychrometer, from its simplicity and the facility with which
it is observed and transported, is almost universally employed for meteoro-
logical observations, both by travellers and at stationary observatories.
The above-given precautions and some practice in its use, are, however,
necessary in order to obtain, reliable results.
Hygrometers acting fy absorption of the vapor.
177. Many organic substances have the property of attracting, by
the force of adhesion, vapor from the atmosphere, and of condensing
it on their surface and in their pores (see 54), by which they increase
their volume or swell. The quantity of vapor which they thus attract or
H 113
114
BOYE'S INANIMATE MATTER.
absorb, varies with, the greater or less proportion, which the quantity of
vapor in the atmosphere forms of the quantity that would constitute satu-
ration, or in other words, with the relative humidity (164), so that
the latter to a certain extent may be measured by the increase or de-
crease of their volume. Of Hygrometers, acting on this principle, only
one deserves a special mention, as giving results which approach to scien-
tific accuracy, viz.
178. Saussure's Hair Hygrometer. It consists of a human hair deprived
of its natural grease by boiling in a feeble solution of carbonate of soda in
water. This hair is suspended in a metallic frame c Jig. 78, the one end
of the hair being attached to a bracket a, which may be adjusted by a
screw; the other end is attached to the circumference of a small wheel or
pulley n. The circumference of this wheel has also another groove, in
Fig. 78. which is fastened and slightly wound around it in the opposite
direction, a thin silk thread, to which is attached a small
weight w, which therefore constantly keeps the hair tense.
It will easily be seen, that when the hair by increased
moisture of the atmosphere absorbs more vapor and thereby
swells, this will be perceptible by its elongation, by which
it allows the weight to turn the wheel. When, on the con-
trary, the humidity of the air diminishes, the hair loses some
of the condensed vapor, it contracts and turns the wheel in
the opposite direction. The axis of the wheel carries a
light index i, which is thus made to traverse a graduated
scale s.
179. To construct the scale of this instrument, it is first placed in a
close receiver, the bottom of which is covered with water and the sides
moistened, by which the air becomes saturated with vapor. The length
of the hair having been so adjusted, that the index will then be near
the one end of the scale, the point where it then stands, as soon as it
becomes stationary, is marked 100, and corresponds to saturation or a
relative humidity of 100. It is then placed, after the removal of the
water, in the same close receiver over oil of vitriol, which deprives the air
of all the vapor ; and the point on the scale where the index then stands,
after it has become almost stationary, is marked 0, which point corre-
sponds to a relative humidity of 0. The distance between and 100 is
divided into 100 equal parts, each of which is called 1 degree. These
degrees do, however, not correspond to the same numbers of relative
humidity. The following table has been given as indicating the differ-
ent relative humidities corresponding to the different degrees of this
hygrometer :
PNEUMATICS.
115
Table of Relative Humidities corresponding to the degrees of Saussure 9 s Hygrometer.
ssure's 1
rometer.l
> *?
ssure's 1
ometei.I
li'
||
>'$
fj
If
If
' 'H
ssure's 1
roineter.l
'3
if
it
oineter.|
II
ssure's 1
rometer.l
If
ssure s 1
rometer 1
If
H
H
II
^a
!
1|
H
II
II
II
I
l
1
a a
l|
II
2|
l|
*l
10
5
20
12
30
19
40
"if
80
35
60
44
70
56
80
69
90
83
1
11
6
21
12
31
20
41
27
51
36
61
45
71
57
81
70
91
85
2
1
12
6
22
13
32
21
42
28
52
37
62
46
72
58
82
72
92
87
3
1
13
7
23
14
33
22
48
28
53
37
63
47
73
59
83
73
93
88
4
2
14
8
24
15
34
23
44
29
54
38
64
49
74
61
84
-9fr
94
90
5
3
15
8'
S>
16
35
24
45
30
55
39
65
^
^5
62
85
77
95
91
6
3
16
9
26
17
36
24
46
31
56
40
66
51
76
63
86
78
96
93
7
4
17
10
27
18
37-
&r
47
32
57
41
67
52
77
65
87
79
97
95
8
4
18
11
28
18
38
26
48
33
58
42
68
53
78
66
88
81
98
97
9
5
19
11
29
19
39
26
49
34
59
43
09
55
79
68
89
82
99
98
180. But this instrument is not so uniform, that the above comparison
can be relied on.
Saussure's directions (Essais surl'Hygrometrie, par B. H. de Saussure, Neufchatel, 1783)
are : to select fine, soft, not curly, nor splitting hair, cut from the head of a living and sane
person. A bunch of these of the thickness of a quill is then sewed up between linen, sepa-
rating them as much as possible. They are then boiled for 30 minutes in a solution of
154 grains of Crystallized Carbonate of Soda in 32 oz. (Troy) of Water, which should be
performed in a flask with a long neck, to prevent the evaporation of the water. The bag
is then twice boiled for a few minutes in pure water, cut open, and the hairs again washed
and separated by moving them to and fro in a large vessel with cold water, after which
they are dried in the open air. The hairs should appear clean, soft, polished and trans-
parent, separating easily from each other. If they are rough and adhere, they have either
been boiled too long, or the solution has become too strong by the evaporation of the water.
The length of the hair in the frame should be about 9^ inch. ; the diameter of the pulley
on which it acts 0.2 inch. The index should be light, and with the pulley perfectly balanced
by itself. The extending weight should not exceed 3 grains; if increased to only 9 grains,
the instrument will, after some time, work irregularly. Saussure has also studied the influ-
ence of the temperature on it, and gives a table for reducing its indications to the same
temperature. He asserts that if his directions are strictly adhered to> the instrument will
never vary more than 2 to 3 degrees. By later experiments, Regnault found no greater
difference with the same kind of hair, if prepared in one and the same operation ; with
different kinds of hair, also prepared in the same operation, the difference amounted to
nearly 5; about the same difference (5) was produced with the same kind of hair, and
prepared in the same operation, but with small differences in the weights by which the hairs
were extended. But icith different kinds of hair, and prepared in different operations, and
having been in use for different lengths of time, the differences amounted in some cases to 15,
even after the extreme points of the scale had been fixed correctly. Regnault concludes from
this, that it is necessary to construct a table for every instrument, by comparing its degrees
with known relative humidities of the air, which he produces by placing it in a close
receiver with different mixtures of oil of vitriol and water, for which mixtures he has given
an elaborate table of tensions ; and also to test the instrument from time to time when
in use. He also proposes to remove the natural grease by placing the hairs for 24
hours in ether, by which they retain their strength and solidity, and acquire almost the
same sensibility. As by placing the instrument in perfectly dry air in order to fix the 0,
it requires several days to become moderately stationary, and the hair continues to con-
US
116 BOYE'S INANIMATE MATTER.
tract, though much less, even for several months, he considers the state to which it is thus
reduced as unnatural, and therefore permanently injuring its hygrometrical properties.
As the air also never reaches this degree, he proposes, therefore, to drop the present
altogether, and to begin the scale from a point, which corresponds to a relative humidity
of 20, and which is produced in a close receiver at the temperature of 4283 Fah. by the
mixture of oil of vitriol and water, which has the chemical composition of 1 atom of sul-
phuric acid, and 5 atoms of water, being represented by the formula, S0 3 + 5 HO.
".
181. gyroscopes. Many other instruments have been constructed from
other organic substances, acting on the same principle as the hair hygrome-
ter; but all these have no scientific value whatever, as none of them can be
relied upon for indicating the relative humidity, even only approximately.
They are therefore not hygrometers, but horoscopes (from UYPS (hugros),
and ffxoxscu (skopeo), I observe), and as such they may be used with advan-
tage to indicate a mere increase or decrease in the moisture of the atmo-
sphere. Of such may be mentioned, strips or bars of whalebone or wood,
cut across the grain. The former may be reduced to a thin thread or band,
and may be made to act on a wheel with an index in a similar manner as
the hair. All twisted strings made of vegetable fibres, as hempen cords,
or of animal membranes, as cat-gut or violin strings, will swell by moisture
and thus by the increase in their diameter untwist themselves, or, if pre-
vented from this, become shorter by the increased twist. A piece of violin
string, if properly prepared, may thus, by its untwisting, be made to turn
back the hood or cowl from the head of a figure in dry weather and to
replace it in damp weather; or to raise its arm and unfurl an umbrella;
or to turn a lever so as to show alternately through a window or before the
door of a toy-house, two different figures, representing rainy and fine weather.
The beard of the husk around the seed of Sensitive Oats (Avena sensitiva),
is naturally twisted or coiled as a double spiral, so that if one end be
fastened in the centre of a graduated circle, and a light index of straw
attached by sealing-wax to the other, the latter will traverse the circular
scale by the coiling or uncoiling of the beard by the moisture in the air.
The bladder of a rat or squirrel, may also be converted into a hygroscope,
by tying its mouth over the end of an open glass-tube and filling the bladder
and part of the tube with mercury. By the contraction or swelling of the
bladder by the change in moisture, the mercury will rise or fall in the tube.
Whalebone, reduced to the thinness of fine paper, goldbeater's skin, and
thin sheets of gelatine or glue, will show such sensitiveness to moisture,
that if cut into figures, as fishes, etc., and placed in the palm of the hand,
the natural moisture of the latter will cause the side next to it to swell,
and the figure to curl itself up.
116
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TABLE II. Correction for reducing Observed Height of Barom. to Stand. Temp, of 32 Fah.
The Scale being of brass and extending the whole length of instrument. Formula in note to par. 77, p. 49.
Observed
Temp, of
Barom.
Fah.
Observed Height in English Inches.
26.5
27
27.5
2S
28.5
29
29.5
30
30.5
31
+.068
+.069
+.071
+.072
+.073
+.074
+.076
+.077
+.078
+.080
1
.065
.067
.068
.069
.071
.072
.073
.074
.076
.077
2
.063
.064
.066
.067
.068
.069
.070
.072
.073
.074
3
.061
.062
.063
.064
.065
.067
.068
.069
.070
.071
4
.058
.059
.061
.062
.063
.064
.065
.066
.067
.068
5
.056
.057
.058
.059
.060
.061
.062
.063
.065
.066
6
+.054
+.055
+.056
+.057
+.058
+.059
+.060
+.061
+.062
+.063
7
.051
.052
.053
.054
.055
.056
.057
.058
.059
.060
8
.049
.050
.051
.052
.053
.054
.054
.055
.056
.057
9
.046
.047
.048
.049
.050
.051
052
.053
.054
.054
10
.044
.045
.046
.047
.047
.048
.049
.050
.051
.052
11
+.042
+.042
+ .043
+.044
+.045
+.046
+.046
+.047
+.048
+.049
12
.039
.040
.041
.042
.042
.043
.044
.045
.045
.046
13
.037
.038
.038
.039
.040
.040
.041
.042
.043
.043
14
.035
.035
.036
.037
.037
.038
.038
.039
.040
.040
15
.032
.033
.033
.034
.035
.035
.036
.036
.037
.038
16
+.030
+.030
+.031
+.032
+.032
+.033
+.033
+.034
+.034
+.035
17
.027
.028
.028
.029
.030
.030
.031
.031
.032
.032
18
.025
.025
.026
.026
.027
.027
.028
.028
.029
.029
19
.023
.023
.024
.024
.024
.025
.025
.026
.026
.027
20
.020
.021
.021
'.021
.022
.022
.023
.023
.023
.024
21
22
+.018
.016
+.018
.016
+.019
.016
4-.019
.016
-L.019
.017
+.020
.017
+.020
.017
+.020
.018
+.021
.018
+.021
.018
23
.013
.013
.014
.014
.014
.014
.015
.015
.015
.015
. 24
.011
.011
.011
.011
.012
.012
.012
.012
.012
.013
25
.008
.009
.009
.009
.009
.009
.009
.009
.010
.010
26
27
+.006
.004
+.006
.004
+.006
.004
+.006
.004
+.006
.004
+.007
.004
+.007
.004
+.007
.004
+.007
.004
+.007
.004
28
.001
.001
.001
.001
.001
.001
.001
.001
.001
.001
29
.001
.001
.001
.001
.001
.001
.001
.001
.001
001
30
.004
.004
.004
.004
.004
.004
.004
.004
.004
.004
31
.006
.006
.006
.006
.006
.007
.007
.007
007
.007
32
.008
.008
.009
.009
.009
.009
.009
009
.010
.010
33
.011
.011
.011
.011
.012
.012
.012
.012
.012
.012
34
.013
.013
.014
.014
.014
.014
.015
.015
.015
.015
35
.015
.016
.016
.016
.017
.017
.017
.018
.018
.018
36
.018
-.018
.019
.019
.019
.020
.020
.020
021
.021
37
.020
.021
.021
.021
.022
.022
.022
.023
.023
.024
38
.023
.023
.023
.024
.024
.025
.025
.026
.026
.026
39
.025
.025
.026
.026
.027
.027
.028
.028
.029
.029
40
.027
.028
.028
.029
.029
.030
.030
.031
.031
.032
41
.030
.030
.031
.031
.032
.033
.033
.034
.034
.035
42
.032
.033
.033
.034
.034
.035
.036
.036
.037
.037
43
.034
.035
.036
.036
.037
.038
.038
.034
.040
.040
44
.037
.037
.038
.039
.040
.040
.041
.042
.042
.043
45
,039
.040
.041
.041
.042
.043
.044
.044
.045
.046
46
.042
.042
.043
.044
.045
.045
.046
.047
.048
.049
47
.044
.045
.046
.046
.047
.048
.049
.050
.051
.051
48
.046
.047
.048
.049
.050
.051
.052
.052
.053
.054
49
.049
.050
.050
.051
.052
.053
.054
.055
.056
.057
50
.051
.052
.053
.054
.055
.056
.057
.058
.059
.060
TABLE II. Correction for reducing Observed Height of Barom. to Stand. Temp, of 32 Fah.
Tha Scale being of brass and extending the whole length of instrument. Formula in note to par. 77, p. 49.
Observed
Temp, of
Baroin.
Fall.
Observed Height In Knglish Inches.
26.5
27
27.5
28
28.5
29
29.5
30
30.5
31
51
.053
.054
.055
.056
.057
.058
.059
.060
.061
.062
52
.056
.057
.058
.059
.060
.061
.062
.063
.064
.065
53
.058
.059
.060
.061
.063
.064
.065
.066
.067
.068
54
.060
.062
.063
.064
.065
.066
.067
.068
.070
.071
55
.063
.064
.065
.066
.068
.069
.070
.071
.072
.073
56
.065
.066
.068
.069
.070
.071
.073
.074
.075
.076
57
.068
.069
.070
.071
.073
.074
.075
.076
.078
.079
58
.070
.071
.073
.074
.075
.077
.078
.079
.081
.082
59
.072
.074
.075
.076
.078
.079
.080
.082
.083
.085
60
.075
.076
.077
.079
.080
.082
.083
.085
.086
.087
61
.077
.078
-.080
.081
.083
.084
.086
.087
.089
.090
62
.079
.081
.082
.084
.085
.087
.088
.090
.091
.093
63
.082
.083
.085
.086
.088
.089
.091
.093
.094
.096
64
.084
.086
.087
.089
.090
.092
.094
.095
.097
.098
65
.086
.088
.090
.091
.093
.095
.096
.098
.100
.101
66
.089
.090
.092
.094
.096
.097
.099
.101
.102
.104
67
.091
.093
.095
.096
.098
.100
.102
.103
.105
.107
68
.094
.095
.097
.099
.101
.102
.104
.106
.108
.109
69
.096
.098
.100
.101
.103
.105
.107
.109
.110
.112
70
.098
.100
.102
.104
.106
.108
.109
.111
.113
.115
71
.101
.102
.104
.106
.108
.110
.112
114
.116
118
72
.103
.105
.107
.109
.111
.113
.115
.117
.119
.120
73
.105
.107
.109
.111
.113
.115
.117
.119
.121
.123
74
.108
.110
.112
.114
.116
.118
.120
.122
.124
.126
75
.110
.112
.114
.116
.118
.120
.122
.125
.127
.129
76
.112
.114
.117
.119
.121
123
.125
_.127
.129
.131
77
.115
.117
.119
.121
.123
.126
.128
.130
.132
.134
78
.117
.119
.122
.124
.126
.128
.130
.133
.135
.137
79
.118
.122
.124
.126
.128
.131
.133
.135
.137
.140
80
.122
.124
.126
.129
.131
.133
.136
.138
.140
.143
81
.124
.126
.129
.131
.134
.136
.138
141
.143
.145
82
.126
.129
.131
.134
.136
.138
.141
.143
.146
.148
83
.129
.131
.134
.136
.139
.141
.143
.146
.148
.151
84
.131
.134
.136
.139
.141
.144
.146
.149
.151
.154
85
.133
.136
.139
.141
.144
.146
.149
.151
.154
.156
86
_.136
.138
.141
.144
.146
.149
.151
.154
.156
.159
87
.138
.141
.143
.146
.149
.151
.154
.157
.159
.162
88
.141
.143
.146
.149
.151
.154
.157
.159
.162
.165
89
.143
.146
.148
.151
.154
.156
.159
.162
.165
.167
90
.145
.148
.151
.153
.156
.159
.162
.164
.167
.170
91
_.148
.150
.153
.156
.159
.162
.165
167
.170
.173
92
.150
.153
.156
.158
.161
.164
.167
.170
.172
.175
93
.152
.155
.158
.161
.164
.167
.170
.172
.175
.178
94
.155
.157
.161
.163
.166
.169
.172
.175
.177
.180
95
.157
.160
.163
.166
.169
.172
.175
.178
.180
.183
96
159
.162
.165
.168
.171
.174
.178
.181
-.183
.186
97
.162
.165
.168
.171
.174
.177
.180
.183
.186
.189
98
.164
.167
.170
.173
.176
.179
.183
.186
.188
.191
99
.166
.169
.173
.176
.179
.182
.185
.188
.191
.194
100
.169
.172
.175
.178
.181
.184
.188
.191
.194
.197
TABLE III. Giving the different distances from the uppermost accessible limit of
the Atmoa. (5.7 miles) corresponding to the different heights of the Barom.
The temp, of the Atmosphere being 32. See Pn. par. 95, page 67.*
3arom.
inches.
Distances
in Feet.
Diff.
with pro-
portional
Barom.
[nches.
Distances
in Feet.
Diff.
with pro-
portional
parts for
thou-
sandths
of Inches
Barom.
Inches.
Distances
in Feet.
Diff.
with pro-
portional
parts for
thou-
sandths
of Inches.
28.00
.01
.02
.03
.04
.05
.06
.07
.08
.09
28.10
.11
.12
.13
.14
.15
.16'
.17
.18
.19
28.20
.21
.22
.23
.24
.25
.26
.27
.28
.29
28.30
.31
.32
.33
.34
.35
.36
.37
.38
.39
28.40
.41
.42
.43
.44
.45
.46
.47
.48
.49
27425-3
27434-6
27444-0
27453-3
27462-6
27471-9
27481-3
27490-6
27499-9
27509-2
27518-4
27527-7
27537-0
27546-3
27555-6
27564-9
27574-2
27583-5
27592-7
27602-0
27611-3
27620-6
27629-8
27639-1
27648-3
27657-6
27666-8
27676-1
27685-3
27694-6
27703-7
27712-9
27722-2
27731-4
27740-6
27749-8
27759-1
27768-3
27777-5
27786-7
27795-8
27805-0
27814-2
27823-4
27832-6
27841-8
27851-0
27860-2
27869-3
27878-5
parts for
thou-
sandths
of laches
28.50
.51
.52
.53
.54
.55
.56
.57
.58
.59
28.60
.61
.62
.63
.64
.65
.66
.67
.68
.69
28.70
.71
.72
.73
.74
.75
.76
.77
.78
.79
28.80
.81
.82
.83
.84
.85
.86
.87
.88
.89
28.90
.91
.92
.93
.94
.95
.96
.97
.98
.99
27887-7
27896-9
27906-0
27915-2
27924-3
27933-5
27942-6
27951-8
27960-9
27970-1
27979-2
27988-3
27997-5
28006-6
28015-7
28024-8
28034-0
28048-1
28052-2
28061-3
28070-5
28079-6
28088-7
28097-8
28106-9
28115-9
28125-0
28134-1
28143-2
28152-2
28161-3
28170-4
28179-4
28188-5
28197-5
28206-6
28215-6
28224-7
28233-7
28242-8
28251-8
28260-8
28269-9
28278-9
28287-9
28296-9
28306-0
28315-0
28324-0
28333-0
29.00
.01
.02
.03
.04
.05
.06
.07
.08
.09
29.10
.11
.12
.13
.14
.15
.16
.17
.18
.19
29.20
.21
.22
.23
.24
.25
.26
.27
.28
.29
29.30
.31
.32
.33
.34
.35
.36
.37
.38
.39
29.40
.41
.42
.43
.44
.45
.46
.47
.48
.49
28342-1
28351-1
28360-1
28369-1
28378-1
28387-1
28396-1
28405-0
28414-0
28423-0
28432-0
28441-0
28450-0
28458-9
28467-9
28476-9
28485-8
28494-8
28503-8
28512-7
28521-7
28530-6
28539-6
28548-5
28557-5
28566-4
28575-4
28584-3
28593-2
28602-2
28611-1
28620-0
28628-9
28637-8
28646-7
28655-6
28664-5
28673-4
28682-3
28691-2
28700-0
28708-9
28717-8
28726-6
28735-5
28744-4
28763-3
28762-1
28771-0
28779-9
9.4
9.1
9.0
1
2
3
4
5
6
7
8
9
0.9
1.9
2.8
3.8
4,7
5.6
6.6
7.5
8.5
1
2
3
4
5
6
7
8
9
0.9
1.8
2.7
3.6
4.6
5.5
6.4
7.3
8.2
1
2
3
4
5
6
N
8
8
0.9
1.8
2.7
3.6
4.5
5.4
6.3
7.2
8.1
9.3
9.0
8.9
1
2
3
4
5
6
7
8
9
0.9
1.9
2.8
3.7
4.7
5.6
6.5
7.4
8.4
9.2
1
2
3
4
5
6
7
8
9
0.9
1.8
2.7
3.6
4.5
5.4
6.3
7.2
8.1
1
2
8
4
5
6
7
8
9
0.9
1.8
2.7
3.6
4.5
5.5
6.2
7.1
8.0
1
2
8
4
5
8
7
8
0.9
1.8
2.8
3.7
4.6
5.5
6.4
7.4
8.3
* The distances in this Table have been obtained by deductini
refer to the upper sensible limit (about 17 miles above the earth).
4
59633.6 feet from those given by the formula, which
TABLE III (Continued). Giving the different distances from the uppermost accessible limit of
the Atmo*. (5.7 miles) corresponding to the different heights of the Barom.
The temp, of the Atmosphere being 32. See Pn. par. 95, page 67.*
Barom.
Inches.
Distances
in Feet.
Diff.
with pro-
portional
parts for
thou-
sandths
of Inch.
Barom.
Inches.
Distances
in Feet.
Diff.
with pro-
portional
parts for
thou-
sandths
of Inch.
Barom.
Inches.
Distances
in Feet.
Diff.
with pro-
portional
parts for
thou-
sandths
of Inch.
29.50
.51
.52
.53
.54
.55
.56
.57
.58
.59
29.60
.61
.62
.63
.64
.65
.66
.67
.68
.69
29.70
.71
.72
.73
.74
.75
.76
.77
.78
.79
29.80
.81
.82
.83
.84
.85
.86
.87
.88
.89
29.90
.91
.92
.93
.94
.95
.96
.97
.98
.99
28788-7
28797-5
28806-4
28815-2
28824-1
28832-9
28841-8
28850-6
28859-4
28868-3
28877-1
28885-9
28894-7
28903-6
28912-4
28921-2
28930-0
28938-8
28947-6
28956-4
28965-2
28974-0
28982-8
28991-6
29000-4
29009-1
29017-9
29026-7
29035-5
29044-2
29053-1
29061-9
29070-6
29079-4
29088-1
29096-9
29105-6
29114-4
29123-1
29131-9
29140-6
29149-3
29158-1
29166-8
29175-5
29184-2
29193-0
29201-7
29210-4
29219-1
30.00
.01
.02
.03
.04
.05
.06
.07
.08
.09
30.10
.11
.12
.13
.14
.15
.16
.17
.18
.19
30.20
.21
.22
.23
.24
.25
.26
.27
.28
.29
30.30
.31
.32
'.83
.34
.35
.36
.37
.38
.39
30.40
.41
.42
.43
.44
.45
.46
.47
.48
49
29227-8
29236-5
29245-2
29253-9
29262-6
29271-3
29280-0
29288-7
29297-3
29306-0
29314-7
29323-4
29332-0
29340-7
29349-3
29358-0
29366-7
29375-3
29384-0
29392-6
29401-3
29409-9
29418-6
29427-2
29435-9
29444-5
29453-2
29461-8
29470-4
29479-1
29487-7
29496-3
29504-9
29513-6
29522-2
29530-8
29539-4
29548-0
29556-6
29565-2
29573-8
29582-4
29591-0
29599-6
29608-2
29616-7
29625-3
29633-9
29642-5
29651-0
30.50
.51
.62
.53
.54
.55
.56
.57
.58
.59
30.60
.61
.62
.63
.64
.65
.66
.67
.68
.69
30.70
.71
.72
.73
.74
.75
.76
.77
.78
.79
0.80
.81
.82
.83
.84
.85
.86
.87
.88
.89
30.90
.91
.92
.93
.94
.95
.96
.97
.98
.99
29659-6
29668-1
29676-7
29685-2
29693-8
29702-3
29710-9
29719-4
29727-9
29736-5
29745-0
29753-5
29762-1
29770-6
29779-1
29787-6
29796-2
29804-7
29813-2
29821-7
29830-2
29838-7
29847-2
29855-7
29864-2
29872-7
29881-2
29889-7
29898-2
29906-7
29915-2
29923-7
29932-2
29940-7
29949-2
29957-6
29966-1
29974-6
29983-5
29991-1
30000-0
30008-5
30016-9
30025-4
300338
30042-3
30050-7
30059-2
30067-6
30076-1
8.9
8.7
8.6
1
2
3
4
5
6
7
8
9
0.9
1.8
2.7
3.6
4.5
5.3
6.2
7.1
8.0
1
2
3
4
5
6
7
8
9
0.9
1.7
2.6
3.5
4.4
5.2
6.1
7.0
7.8
1
2
3
4
5
6
7
8
9
0.9
1.7
2.6
3.4
4.3
5.2
6.0
6.9
7.7
8.8
8.6
8.5
1
2
3
4
6
6
7
8
9
0.9
1.8
2.6
3.5
4.4
5.3
6.2
7.0
7.9
1
2
8
4
5
6
7
8
9
0-9
1.7
2.6
3.4
4.3
5.1
6.0
6.8
7.7
8.7
8.4
1
2
&
.(
B
(3
7
8
I
0.9
1.7
2.6
3.5
4.4
5.2
6.1
7.0
7.8
]
2
3
4
5
6
7
8
9
0.9
1.7
2.6
3.4
4.3
5.2
6.0
6.9
7.7
1
2
3
4
5
(i
7
s
y
0.8
1.7
2.5
3.4
4.2
5.0
5.9
6.7
7.6
* To avoid too large numbers, the distances in this Table have not been referred to the upper sensible limit (17 miles),
but to the uppermost accessible limit (5.7 miles), by deducting 5%:)3.6 feet from those obtained by the indicated method.
5
TABLE IV. Correction for Latitude, on account of Decrease of Gravity from Pole to Equator.
To be applied to Height obtained from Barometric Observations, see par. 95, page 68.
ADD this correction if Lat. less than 43 ; DEDUCT if Lat. greater than 45.
Latitude.
Obtained Height.
1 Foot.
2 Feet.
3 Feet.
4 Feet.
5 Feet.
6 Feet.
7 Feet.
8 Feet.
J Feet.
Thou-
Thou-
Thou-
Thou-
Thou-
Thou-
Thou-
Thou-
Thou-
Deduct
sandths
sandths
sandths
sandths
sandths
sandths
sandths
sandths
sandths
k du for.
for.
of Feet.
of Feet.
of Feet.
of Feet.
of Feet.
of Feet.
of Feet.
of Feet.
of Feet.
90
2.837
5.674
8.511
11.348
14.186
17.023
19.860
22.697
25.534
1
89
2.835
5.671
8.506
11.342
14.177
17.012
19.848
22.683
25.518
2
88
2.830
5.660
8.491
11.321
14.151
16.981
19.811
22.642
25.472
3
87
2.822
5.643
8.465
11.286
14.108
16.929
19.751
22.573
25.394
4
86
2.810
5.619
8.429
11.238
14.047
16.857
19.666
22.476
25.285
5
85
2.794
5.588
8.382
11.176
13.970
16.764
19.558
22.352
25.146
6
84
2.775
5.550
8.325
11.100
13.876
16.651
19.426
22.201
24.976
7
83
2.753
5.506
8.259
11.011
13.764
16.517
19.270
22.023
24.775
8
82
2.727
5.454
8.182
10.909
13.636
16.363
19.090
21.818
24.545
9
81
2.698
5.397
8.095
10.793
13.491
16.190
18.888
21.586
24.284
10
80
2.666
5.332
7.998
10.664
13.330
15.996
18.662
21.328
23.994
11
79
2.631
5.261
7.892
10.522
13.153
15.783
18.413
21.044
23.675
12
78
2.592
5.184
7.776
10.367
12.959
15.551
18.142
20.735
23.326
13
77
2.550
5.100
7.650
10.200
12.750
15.300
17.850
20.400
22.950
14
76
2.505
5.010
7.515
10.020
12.525
15.033
17.535
20.040
22.545
15
75
2.457
4.914
7.371
9.828
12.285
14.742
17.199
19.656
22.113
16
74
2.406
4.812
7.218
9.624
12.030
14.436
16.842
19.248
21.654
17
73
2.352
4.704
7.056
9.408
11.760
14.112
16.464
18.817
21.169
18
72
2.295
4.591
6.886
9.181
11.476
13.772
16.067
18.362
20.657
19
71
2.236
4.471
6.707
8.943
11.178
13.414
15.650
17.885
20.121
20
70
2.173
4.347
6.520
8.693
10.867
13.040
15.213
17.387
19.560
21
69
2.108
4.217
6.325
8.434
10.542
12.650
14.759
16.867
18.975
22
68
2.041
4.082
6.123
8.163
10.204
12.245
14.286
16.327
18.368
23
67
1.971
3.942
5.912
7.883
9.854
11.825
13.796
15.767
17.737
24
66
1.898
3.797
5.695
7.594
9.492
11.390
13.289
15.187
17.086
25
65
1.824
3.647
5.471
7.295
9.118
10.942
12.766
14.589
16.413
26
64
1.747
3.493
5.240
6.987
8.734
10.480
12.227
13.974
15.720
27
63
1.668
3.335
5.003
6.670
8.338
10.006
11.673
13.341
15.008
28
62
1.587
3.173
4.756
6.346
7.932
9.519
11.105
12.692
14.278
29
61
1.503
3.007
4.510
6.014
7.517
9.021
10.524
12.028
13.531
30
60
1.419
2.837
4.256
5.674
7.093
8.511
9.930
11.348
12.767
31
59
1.332
2.664
3.996
5.328
6.660
7.992
9.324
10.656
11.987
32
58
1.244
2.487
3.731
4.975
6.218
7.462
8.706
9.950
11.193
33
57
1.154
2.308
3.462
4.616
5.770
6.924
8.078
9.232
10.386
34
56
1.063
2.126
3.188
4.251
5.314
6.377
7.440
8.502
9.565
35
55
0.970
1.941
2.911
3.881
4.852
5.822
6.792
7.763
8.733
36
54
0.877
1.753
2.630
3.507
4.384
5.260
6.137
7.014
7.890
37
53
0.782
1.564
2.346
3.128
3.910
4.692
5.474
6.256
7.038
38
52
0.686
1.373
2.059
2.745
3.432
4.118
4.805
5.491
6.177
39
51
0.590
1.180
1.767
2.360
2.949
3.539
4.129
4.719
5.309
40
50
0.493
0.985
1.478
1.971
2.463
2.956
3.449
3.941
4.434
41
49
0.395
0.790
1.184
1.579
1.974
2.369
2.764
3.159
3.554
42
48
0.297
0.593
0.890
1.186
1.483
1.779
2.076
2.372
2.669
43
47
0.198
0.396
0.594
0.792
0.990
1.187
1.385
1.583
1.781
44
46
0.099
0.198
0.297
0.396
0.495
0.594
0.693
0.792
0.891
45
45
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
TABLE V. Correction for Altitude, on account of Decrease of Gravity from level of sea upward
into the Atmoa. To be applied to Height obtained from Barom. Observ., see par, 95, p. 68.
Obtained
Height
in Feet.
Correc. to
be added.
Feet.
Obtained
Height
in Feet.
Correc. to
be added.
Feet.
Obtsiind
Height
in Feet.
Correc. to
be added.
Feet.
Obtain'd
Height
in Feet.
Correc. to
be added.
Feet.
Obtain'd
Height
in Feet.
Dorrec. to
be added.
Feet.
200
0.502
5200
14.303
10200
30.492
15200
49.087
20200
69.876
400
1.008
5400
14.905
10400
31.196
15400
49.880
20400
70.959
600
1.518
5600
15.511
10600
31.897
15600
50.677
20600
71.851
800
2.032
5800
16.120
10800
32.602
15800
51.478
20800
72.748
1000
2.550
6000
16.734
11000
33.312
16000
52.282
21000
73.649
1200
3.071
6200
17.351
11200
34.024
16200
53.092
21200
74.553
1400
3.596
6400
17.972
11400
34.741
16400
53.904
21400
75.461
1600
4.125
6600
18.597
11600
35.462
16600
54.721
21600
76.374
1800
4.658
6800
19.225
11800
36.186
16800
55.541
21800
77.289
2000
5.195
7000
19.858
12000
36.914
17000
56.365
22000
78.209
2200
5.735
7200
20.494
12200
37.646
17200
57.193
22200
79.133
2400
6.280
7400
21.134
12400
38.382
17400
58.024
22400
80.060
2600
6.828
7600
21.778
12600
39.122
17600
58.860
22600
80.991
2800
7.380
7800
22.426
12800
39.866
17800
59.699
22800
81.926
3000
7.936
8000
23.733
13000
40.613
18000
60.542
23000
82.865
3200
8.496
8200
24.165
13200
41.364
18200
61.389
23200
83.808
3400
9.059
8400
24.392
13400
42.119
18400
62.240
23400
84.755
3600
9.627
8600
25.055
13600
42.878
18600
63.095
23600
85.705
3800
10.198
8800
25.722
13800
43.641
18800
63.953
23800
86.659
4000
10.773
9000
26.393
14000
44.407
19000
64.815
24000
87.617
4200
11.352
9200
27.068
14200
45.177
19200
65.681
24200
88.579
4400
11.934
9400
27.746
14400
45.952
19400
66.565
24400
89.545
4600
12.521
9600
28.428
14600
46.730
19600
67.425
24600
90.514
4800
13.111
9800
29.115
14800
47.512
19800
68.303
24800
91.488
5000
13.705
10000
29.804
15000
48.297
20000
69.184
25000
92.465
TABLE VI. For the conversion of French into English) and English, into French measures.
French
Millime-
tres.
English
Inches.
English
Inches.
French
Millimetres.
French
Metres.
English
Feet.
English
Feet.
French
Metres.
1
0.03937079
1
25.39954
1
3.2808992
1
0.30479449
2
0.07874158
2
50.79908
2
6.5617984
2
0.60958898
3
0.11811237
3
7&. 19862
3
9.8426976
3
0.91438347
4
0.15748316
4
101.59816
4
13.1235968
4
1.21917796
5
0.19685395
5
126.99770
5
16.4044960
5
1.52397245
6
0.23622474
6
152.39724
6
19.6853952
6
1.82876694
7
0.27559553
7
177.79678
7
22.9662944
7
2.13356143
8
0.31496632
8
203.19632
8
26.2471936
8
2.43835592
9
0.35433711
9
228.59586
9
29.5280928
9
2.74315041
720
28.34697
27
685.78758
1 Paris or old French Foot = 1.065765 English Foot.
730
28.74068
28
711.18712
1 " " " Inch rr 1.065765 " Inch.
740
750
760
29.13438
29.52809
29.92180
29
30
31
736.58666
761.98620
787.38574
1 " " " Line = 0.088814 "
1 French Litre 61.0275 English cubic Inches.
1 Engl. Wine Gallon = 231.044 Engl. cubic Inches.
1 Entrl. cubic Inch 0.00432818 En^l Win fil
1 French Gramme Weight r: ljl433 Engl. grains. 1 Eng. cub. In.:=252.458 Eng. grains of Water of 62.
1 Fr. Kilogramme = 2.2047 Engl. pounds Av.d.p. 1000 Eng. gr's Water of 62 = 3.961054 Eng. cub. In.
TABLE VII. Giving the Maximum Tension or Elastic Force of Vapor of Water
for every 0.2 degree from 214 to 185. Pn. par. 87 page 58, and par. 139 page 94.
Temp.
Fah.
Max. Tens,
nch. Merc.
Differ-
ences.
Temp.
Fah.
Max. Tens,
nch. Merc.
Differ-
ences.
Temp.
Fan.
Max. Tens.
nch. Merc.
Differ-
ences.
214.0
213.8
213.6
213.4
213.2
213.0
31.132
31.009
30.887
30.765
30.643
30.522
0.123
0.122
0.122
0.122
0.121
0.121
204.0
203.8
203.6
203.4
203.2
203.0
25.468
25.364
25.261
25.158
25.055
24.952
0.104
0.103
0.103
0.103
0.103
0.102
194.0
193.8
193.6
193.4
193.2
193.0
20.687
20.600
20.513
20.426
20.340
20.254
0.087
0.087
0.087
0.086
0.086
0.086
212.8
212.6
212.4'
212.2
212.0
30.401
30.281
30.161
30.041
29.922
0.120
0.120
0.120
0.119
0.119
202. 8
202. 6
202. 4
202. 2
202.0
24.850
24.748
24.646
24.545
24.444
0.102
0.102
0.101
0.101
0.101
192.8
192.6
192.4
192.2
192.0
20.168
20.082
19.997
19.912
19.827
0.086
0.085
0.085
0.085
0.084
11
29.803
29.685
29.567
29.449
29.332
0.118
0.118
0.118
0.117
0.117
20P.8
20P.6
20P.4
20P.2
20P.O
24.343
24.243
24.144
24.045
23.946
0.100
0.099
0.099
0.099
0.099
i9i o !e
19P.4
19P.2
19.743
19.659
19.575
19.492
19.409
0.084
0.084
0.083
0.083
0.083
210.8
210. 6
210.4
210.2
210.0
29.215
29.099
28.983
28.868
28.753
0.116
0.116
0.115
0.115
0.115
200.8
200.6
200.4
200.2
200.0
23.847
23.749
23.651
23.553
23.456
0.098
0.098
0.098
0.097
0.097
190. 8
190.6
190.4
190.2
190.0
19.326
19.243
19.161
19.079
18.997
0.083
0.082
0.082
0.082
0.081
209. 8
209.6
209.4
209.2
209.0
28.638
28.524
28.410
28.296
28.183
0.114
0.114
0.114
0.113
0.113
199.8
199.6
199.4
199.2
199.0
23.359
23.262
23.166
23.070
22.974
0.097
0.096
0.096
0.096
0.095
189.8
189.6
189.4
189.2
189.0
18.916
18.835
18.754
18.673
18.593
0.081
0.081
0.081
0.080
0.080
208. 8
208. 6
208.4
208.2
208.0
28.070
27.958
27.846
27.734
27.622
0.112
0.112
0.112
0.112
0.111
198.8
198.6
198.4
198. 2
198.0
22.879
22.784
22.689
22.595
22.501
0.095
0.095
0.094
0.094
0.094
188. 8
188.6
188.4
188.2
188.0
18.513
18.434
18.355
18.276
18.197
0.079
0.079
0.079
0.079
0.079
207. 8
207.6
207.4
207.2
207.0
27.511
27.400
27.290
27.180
27.070
'0.111
0.110
0.110
0.110
0.109
197.8
197.6
197.4
197.2
197.0
22.407
22.313
22.220
22.127
22.035
0.094
0.093
0.093
0.092
0.092
187.8
187.6
187.4
187.2
187.0
18.118
18.040
17.962
17.884
17.807
0.078
0.078
0.078
0.077
0.077
206. 8
206. 6
206.4
206.2
206.0
26.961
26.852
26.743
26.635
26.527
0.109
0.109
0.108
0.108
0.107
196.8
196. 6
196.4
196.2
196.0
21.943
21.851
21.760
21.669
21.578
0.092
0.091
0.091
0.091
0.090
186.8
186.6
186.4
186.2
186,0
o
17.730
17.654
17.578
17.502
17.426
0.076
0.076
0.076
0.076
0.076
205.8
205.6
205. 4
205.2
205.0
26.420
26.313
26.206
26.100
25.994
0.107
0.107
0.106
0.106
0.106
195.8
195.6
195.4
195.2
195.0
21.488
21.398
21.308
21.218
21.128
0.090
0.090
0.090
0.090
0.089
185 8
185.6
185.4
185.2
185.0
17.350
17.274
17.199
17.124
17.049
0.076
0.075
0.075
0.075
204. 8
204. 6
25.888
25.782
0.106
ft -IAK
194.8
194.6
21.039
20.950
0.089
088
204.4
25.677
v. 1UO
194.4
20.862
U.UOo
204. 2
25.572
0.105
104.
194.2
20.774
0.088
087
204.0
25.468
U. J.UTC
194.0
20.687
V. vO t
TABLE VIII. Giving the, Maximum Tension or Elastic Force of Vapor of Water,
for every degree from 185 to 104. Pn. par. 87 page 58, and par. 139 page 94.
Temp.
Fah.
Max. Tens.
Inch. Merc.
Differ-
ences.
Temp.
Fab.
Max. Tens.
Inch. Merc.
Differ-
ences.
Temp.
Fah.
Max. Tens.
Inch. Merc.
Differ-
ences.
185
17.0492
OCQQ
158
9.1770
21Q9
131
4.6252
1221
184
183
182
181
180
179
178
177
176
175
174
173
172
171
170
169
168
167
166
165
164
163
162
161
160
159
16.6804
16.3182
15.9626
15.6135
15.2709
14.9346
14.6045
14.2805
13.9625
13.6504
13.3442
13.0438
12.7491
12.4601
12.1767
11.8988
11.6263
11.3591
11.0971
10.8402
10.5883
10.3413
10.0991
9.8617
9.6289
9.4007
.3622
.3556
.3491
.3426
.3363
.3301
.3240
.3180
.3121
.3062
.3004
.2947
.2890
.2834
.2779
.2725
.2672
.2620
.2569
.2519
.2470
.2422
.2374
.2328
.2282
.2237
157
156
155
154
153
152
151
150
149
148
147
146
145
144
143
142
141
140
139
138
137
136
135
134
133
132
8.9578
8.7431
8.5328
8.3269
8.1253
7.9281
7.7349
7.5456
7.3602
7.1787
7.0010
6.8271
6.6568
6.4901
6.3269
6.1672
6.0109
5.8580
5.7084
5.5621
5.4190
5.2791
5.1423
5.0086
4.8779
4.7501
.2147
.2103
.2059
.2016
.1972
.1932
.1893
.1854
.1815
.1777
.1739
.1703
.1667
.1632
.1597
.1563
.1529
.1496
.1463
.1431
.1399
.1368
.1337
.1307
.1278
.1249
130
129
128
127
126
125
124
123
122
121
120
119
118
117
116
115
114
113
112
111
110
109
108
107
106
105
4.5031
4.3838
4.2673
4.1534
4.0421
3.9334
3.8273
3.7237
3.6214
3.5224
3.4257
3.3313
3.2392
3.1493
3.0615
2.9758
2.8922
2.8107
2.7313
2.6538
2.5782
2.5044
2.4324
2.3622
2.2937
2.2269
.1193
.1165
.1139
.1113
.1087
.1061
.1036
.1013
.0990
.0967
.0944
.0921
.0899
.0878
.0857
.0836
.0815
.0794
.0775
.0756
.0738
.0720
.0702
.0685
.0668
.0652
TABLE IX. Giving the Maximum Tension or Elastic Force of Vapor of Water,
for every 0.2 degree from 104 to 0, and for every degree from to 31.
Temp.
Fah.
Max. Tens.
Inch. Merc.
Differ-
ences.
Temp.
Fah.
Max. Tens.
Inch. Merc.
Differ-
ences.
Temp.
Fah.
Max. Tens.
Inch. Merc.
Differ-
ences.
104.0
103.8
103. 6
103.4
103.2
103.0
102.8
102.6
102.4
102.2
102.0
101.8
101.6
101.4
101.2
101.0
100.8
100.6
100.4
100.2
100.0
2.1617
2.1489
2.1362
2.1235
2.1109
2.0983
2.0858
2.0734
2.0611
2.0488
2.0366
2.0244
2.0123
2.0003
1.9883
1.9764
1.9646
1.9528
1.9411
1.9294
1.9178
.0128
.0127
.0127
.0126
.0126
.0125
.0124
.0123
.0123
.0122
.0122
.0121
.0120
.0120
.0119
.0118
.0118
.0117
.0117
.0116
100.0
99.8
99.6
99.4
9-9. 2
99.0
98.8
98.6
98.4
98.2
98.0
97.8
97.6
97.4
97.2
97.0
96. 8
96. 6
96. 4
96.2
96.0
1.9178
1.9063
1.8948
1.8833
1.8719
1.8606
1.8494
1.8382
1.8271
1.8161
1.8051
1.7942
1.7833
1.7724
1.7616
1.7509
1.7402
1.7296
1.7190
1.7085
1.6981
.0115
.0115,
.0115
.0114
.0113
.0112
.0112
.0111
.0110
.0110
.0109
.0109
.0109
.0108
.0107
.0107
.0106
.0106
.0105
.0104
96.0
95. 8
95.6
95.4
95.2
95.0
94. 8
94. 6
94. 4
94. 2
94.0
93.8
93.6
93.4
93.2
93.0
92.8
92. 6
92.4
92.2
92.0
1.6981
1.6878
1.6775
1.6672
1.6570
1.6468
1.6366
1.6265
1.6165
1.6066
1.5967
1.5869
1.5771
1.5674
1.5577
1.5480
1.5384
1.5289
1.5194
1.5100
1.5006
.0103
.0103
.0103 I
.0102
.0102
.0102
.0101
.0100
.0099
.0099
.0098
.0098
.0097
.0097
.0097
.0096
.0095
.0095
.0094
.0094
TABLE IX (Continued). Giving the Maximum Tension or Elastic Force of Vapor of Water.
Temp.
Fah.
Max. Tens.
Inch. Merc.
UifllT-
ences.
Temp.
Fah
Max. Tens,
nch. Merc.
Diiler-
ences.
Temp.
Fah
Max. Tens,
nch. Merc.
DilTer-
ences.
92.0
91.8
91.6
91.4
91.2
91.0
90.8
90. 6
90.4
90.2
90.0
89.8
89.6
89.4
89.2
89.0
88. 8
88. 6
88. 4
88.2
88.0
87.8
87.6
87.4
87.2
87.0
86. 8
86. 6
86.4
86.2
86.0
85.8
85.6
85.4
85.2
85.0
84. 8
84.6
84. 4
84. 2
84.0
83.8
83.6
83. 4
83.2
83.0
82. 8
82. 6
82.4
82. 2
82.0
81.8
81.6
81.4
81.2
81.0
1.5006
1.4913
1.4821
1.4729
1.4637
1.4545
1.4454
1.4364
1.4274
1.4185
1.4096
1.4008
1.3921
1.3834
1.3747
1.3661
1.3575
1.3489
1.3404
1.3319
1.3235
1.3152
1.3069
1.2986
1.2904
1.2822
1.2741
1.2660
1.2580
1.2500
1.2421
1.2342
1.2263
1.2185
1.2107
1.2030
1.1953
1.1877
1.1801
1.1726
1.1651
1.1576
1.1502
1.1428
1.1354
1.1281
1.1208
1.1136
1.1064
1.0993
1.0922
1.0851
1.0781
1.0711
1.0641
1.0572
.0093
.0092
.0092
.0092
.0092
.0091
.0090
.0090
.0089
.0089
.0088
.0087
.0087
.0087
.0086
.0086
.0086
.0085
.0085
.0084
.0083
.0083
.0083
.0082
.0082
.0081
.0081
.0080
.0080
.0079
.0079
.0079
.0078
.0078
.0077
.0077
.0076
.0076
.0075
.0075
.0075
.0074
.0074
.0074
.0073
.0073
.0072
.0072
.0071
.0071
.0071
.0070
.0070
.0070
.0069
81.0
80.8
80. 6
80.4
80.2
80.0
79.8
79.6
79.4
79.2
79.0
78. 8
78.6
78.4
78.2
78.0
77.8
77.6
77.4
77.2
77.0
76.8
76.6
76.4
76.2
76.0
75.8
75.6
75.4
75.2
75.0
74.8
74.6
74. 4
74.2
74.0
73.8
73.6
,73.4
73.2
73.0
72.8
72.6
72.4
72.2
72.0
71.8
71.6
71.4
71.2
71.0
70.8
70.6
70, 4
70.2
70.0
1.0572
1.0503
1.0435
1.03G7
1.0300
1.0233
1.0166
1.0100
1.0034
0.9968
0.9903
0.9838
0.9774
0.9710
0.9646
0.9583
0.9520
0.9457
0.9395
0.9333
0.9272
0.9211
0.9150
0.9089
0.9028
0.8968
0.8909
0.8850
0.8792
0.8734
0.8676
0.8618
0.8560
0.8503
0.8446
0.8390
0.8334
0.8279
0.8224
0.8169
0.8114
0.8060
0.8006
0.7952
0.7898
0.7845
0.7792
0.7740
0.7688
0.7636
0.7585
0.7534
0.7483
0.7432
0.7381
0.7331
.0069
.0068
.0068
.0067
.0067
.0067
.0066
.0066
.0066
.0065
.0065
.0064
.0064
.0064
.0063
.0063
.0063
.0062
.0062
.0061
.0061
.0061
.0061
.0061
.0060
.0059
.0059
.0058
.0058
.0058
.0058
.0058
.0057
.0057
.0056
.0056
.0055
.0055
.0055
.0055
.0054
.0054
.0054
.0054
.0053
.0053
.0052
.0052
.0052
.0051
.0051
.0051
.0051
.0051
.0050
70.0
69.8
69.6
69.4
69.2
69.0
68.8
68.6
68.4
68.2
68.0
67.8
67.6
67.4
67.2
67.0
66.8
66.6
66.4
66.2
66.0
65.8
65.6
65.4
65.2
65.0
64. 8
64.6
64. 4
64.2
64.0
63.8
63.6
63.4
63.2
63.0
62.8
62.6
62.4
62.2
62.0
61.8
61.6
61.4
6P.2
61.0
60.8
60. 6
60.4
60. 2
60.0
59.8
59.6
59.4
59.2
59.0
0.7331
0.7281
0.7232
0.7183
0.7134
0.7085
0.7036
0.6988
0.6941
0.6894
0.6847
0.6800
0.6754
0.6708
0.6662
0.6616
0.6570
0.6525
0.6480
0.6435
0.6391
0.6347
0.6303
0.6260
0.6217
0.6174
0.6131
0.6088
.0.6046
0.6004
0.5962
0.5921
0.5880
0.5839
0.5798
0.5758
0.5718
0.5678
0.5638
0.5599
0.5560
0.5521
0.5482
0.5443
0.5405
0.5367
0.5329
0.5291
0.5254
0.5217
0.5180
0.5143
0.5107
0.5071
0.5035
0.4999
.0050
.0049
.0049
.0049
.0049
.0049
.0048
.0047
.0047
.0047
.0047
.0046
.0046
.0046
.0046
.0046
.0045
.0045
.0045
.0044
.0044
0044
.0043
.0043
.0043
.0043
.0043
.0042
.0042
.0042
.0041
.0041
.0041
.0041
.0040
.0040
.0040
.0040
.0039
.0039
.0039
.0039
.0039
.0038
.0038
.0038
.0038
.0037
.0037
.0037
.0037
.0036
.0036
.0036
.0036
TABLE IX. (Continued). Giving the Maximum Tension or Elastic Force of Vapor of Water.
Temp.
Fah.
Max. Tens.
Inch. Merc.
Differ-
ences.
Temp.
Fan.
Max. Tens-
Inch. Merc-
Differ-
ences.
Temp.
Fah.
Max. Tens.
Inch. Merc.
Differ-
ences.
59.0
58.8
58.6
58.4
58.2
58.0
57.8
57.6
57.4
57.2
57.0
5G.8
56.6
56.4
56.2
56.0
55.8
55.6
55.4
55.2
55.0
54. 8
54.6
54. 4
54.2
54.0
53.8
53. 6
53.4
53.2
53.0
52.8
52.6
52.4
52.2
52.0
51.8
51.6
51,4
51.2
51.0
50. 8
50.6
50. 4
50. 2
50.0
49.8
49. 6
49.4
49.2
49.0
48. 8
48.6
48.4
48. 2
48.0
0.4999
0.4964
0.4929
0.4894
0.4859
0.4824
0.4790
0.4756
0.4722
0.4688
0.4655
0.4622
0.4589
0.4556
0.4523
0.4491
0.4459
0.4427
0.4395
0.4363
0.4331
0.4299
0.4268
0.4237
0.4207
0.4177
0.4147
0.4117
0.4087
0.4057
0.4028
0.3999
0.3970
0.3941
0.3912
0.3883
0.3855
0.3827
0.3799
0.3771
0.3743
0.3716
0.3689
0.3662
0.3635
0.3608
0.3581
0.3555
0.3529
0.3503
0.3477
0.3451
0.3426
0.3401
0.3376
0.3351
.0035
.0035
.0035
.0035
.0035
.0034
.0034
.0034
.0034
.0033
.0033
.0033
.0033
.0033
.0032
.0032
.0032
.0032
.0032
.0032
.0032
.0031
.0031
.0030
.0030
.0030
.0030
.0030
.0030
.0029
.0029
.0029
.0029
.0029
.0029
.0028
.0028
.0028
.0028
.0028
.0027
.0027
.0027
.0027
.0027
.0027
.0026
.0026
.0026
.0026
.0026
.0025
.0025
.0025
.0025
48.0
47.8
47.6
47.4
47.2
47.0
46. 8
46. 6
46.4
46. 2
46.0
45.8
45.6
45.4
45.2
45.0
44. 8
44. 6
44.4
44.2
44.0
43.8
43.6
43.4
43.2
43.0
42.8
42.6
42.4
42,2
42.0
41.8
41.6
41.4
41.2
41.
40.8
40. 6
40.4
40. 2
40.0
39.8
39.6
39.4
39.2
39.0
38.8
38.6
38.4
38.2
38,0
37.8
37. 6
37.4
37.2
37.0
0.3351
0.3326
0.3301
0.3276
0.3252
0.3228
0.3204
0.3180
0.3156
0.3132
0.3109
0.3086
0.3063
0.3040
0.3017
0.2994
0.2972
0.2950
0.2928
0.2906
0.2884
0.2862
0.2840
0.2818
0.2797
0.2776
0.2755
0.2734
0.2713
0.2692
0.2672
0.2652
0.2632
0.2612
0.2592
0.2572
0.2552
0.2533
0.2514
0.2495
0.2476
0.2457
0.2438
0.2419
0.2400
0.2382
0.2364
0.2346
0.2328
0.2310
0.2292
0.2274
0.2256
0.2239
0.2222
0.2205
.0025
.0025
.0025
.0024
.0024
.0024
.0024
.0024
.0024
.0023
.0023
.0023
.0023
.0023
.0023
.0022
.0022
.0022
.0022
.0022
.0022
.0022
.0022
.0021
.0021
.0021
.0021
.0021
.0021
.0020
.0020
.0020
.0020
.0020
.0020
.0020
.0019
.0019
.0019
.0019
.0019
.0019
.0019
.0019
.0018
.0018
.0018
.0018
.0018
.0018
.0018
.0018
.0017
.0017
.0017
37.
36.8
36.6
36.4
36.2
36.0
35. 8
35.6
35.4
35.2
35.0
34.8
34. 6
34. 4
34.2
34.0
33.8
33.6
33.4
33. 2
33.0
32.8
32.6
32.4
32.2
32.0
31.8
31.6
31.4
31.2
31.0
30. 8
30.6
30.4
30. 2
30.0
29.8
29.6
29.4
29. 2
29.0
28. 8
28.6
28.4
28.2
28.0
27.8
27.6
27.4
27.2
27.0
26.8
26.6
26.4
26.2
26.0
0.2205
0.2188
0.2171
0.2154
0.2137
0.2120
0.2104
0.2088
0.2072
0.2056
0.2040
0.2024
0.2008
0.1992
0.1976
0.1960
0.1944
0.1929
0.1914
0.1899
0.1884
0.1869
0.1854
0.1840
0.1825
0.1811
0.1796
0.1781
0.1766
0.1751
0.1736
0.1722
0.1708
0.1694
0.1680
0.1666
0.1652
0.1638
0.1624
0.1610
0.1596
0.1583
0.1570
0.1557
0.1544
0.1531
0.1518
0.1505
0.1492
0.1479
0.1466
0.1454
0.1442
0.1430
0.1418
0.1406
.0017
.0017
.0017
.0017
.0017
.0016
.0016
.0016
.0016
.0016
.0016
.0016
.0016
.0016
.0016
.0016
.0015
.0015
.0015
.0015
.0015
.0015
.0015
.0015
.0015
.0015
.0015
.0015
.0015
.0015
.0014
.0014
.0014
.0014
.0014
.0014
.0014
.0014
.0014
.0014
.0013
.0013
.0013
.0013
.0013
.0013
.0013
.0013
.0013
.0013
.0012
.0012
.0012
.0012
.0012
TABLE IX. (Continued). Giving the Maximum Tension or Elastic Force of Vapor of Water.
Temp.
Fab.
lax. Tens,
nch. Merc.
Differ-
ences.
Temp.
Fan.
Max. Tens,
nch. Merc.
Differ-
ences.
Temp.
Fah.
Max. Tens,
nch. Merc.
Differ-
ences.
26.0
25.8
25.6
25.4
25.2
25.0
24. 8
24. 6
24. 4
24 2
24.0
23.8
23.6
23.4
23.2
23.0
22.8
22.6
22.4
22 2
22.0
0.1406
0.1394
0.1382
0.1370
0.1358
0.1346
0.1334
0.1322
0.1310
0.1299
0.1288
0.1277
0.1266
0.1255
0.1244
0.1233
0.1222
0.1211
0.1200
0.1189
0.1178
.0012
.0012
.0012
.0012
.0012
.0012
.0012
.0012
.0011
.0011
.0011
.0011
.0011
.0011
.0011
.0011
.0011
.0011
.0011
.0011
0010
15.0
14.8
14.6
14.4
14.2
14.0
13.8
13.6
13.4
13.2
13.0
12.8
12.6
12.4
12.2
12.0
11.8
11.6
11.4
11.2
11.0
0.0858
0.0850
0.0842
0.0834
0.0826
0.0818
0.0810
0.0803
0.0796
0.0789
0.0782
0.0775
0.0768
0.0761
0.0754
0.0747
0.0740
0.0733
0.0726
0.0719
0.0713
.0008
.0008
.0008
.0008
.0008
.0008
.0007
.0007
.0007
.0007
.0007
.0007
.0007
.0007
.0007
.0007
.0007
0007
.0007
.0006
OOOfi
4.0
3.8
3.6
3.4
3.2
3.0
2.8
2.6
2 4
2!2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
o.o
0.0520
0.0515
0.0510
0.0505
0.0500
0.0495
0.0490
0.0485
0.0481
0.0477
0.0473
0.0469
0.0465
0.0461
0.0457
0.0453
0.0449
0.0445
0.0441
0.0437
0.0433
.0005
.0005
.0005
.0005
.0005
.0005
.0005
.0004
.0004
.0004
.0004
.0004
.0004
.0004
.0004
.0004
.0004
.0004
.0004
.0004
21.8
21.6
21.4
21.2
21.0
20. 8
20.6
0.1168
0.1158
0.1148
0.1138
0.1128
0.1118
0.1108
.0010
.0010
.0010
.0010
.0010
.0010
10.8
10.6
10.4
10.2
10.0
9.8
9.6
0.0707
0.0701
0.0695
0.0689
0.0683
0.0677
0.0671
.0006
.0006
.0006
.0006
.0006
.0006
1
2
3
4
5
0.0433
0.0413
0.0394
0.0376
0.0360
0.0344
.0020
.0019
.0018
.0016
.0016
.0016
20. 4
20.2
20.0
19.8
19.6
19.4
19.2
19.0
18.8
18.6
18.4
18.2
18.0
17.8
17.6
17.4
0.1098
0.1088
0.1078
0.1068
0.1058
0.1048
0.1039
0.1030
0.1021
0.1012
0.1003
0.0994
0.0985
0.0976
0.0967
0.0958
.uuiu
.0010
.0010
.0010
.0010
.0010
.0009
.0009
.0009
.0009
.0009
.0009
.0009
.0009
.0009
.0009
9.4
9.2
9,0
8.8
8.6
8.4
8.2
8.0
7.8
7.6
7.4
7.2
7.0
6.8
6. 6
6.4
0.0665
0.0659
0.0653
0.0647
0.0641
0.0635
0.0629
0.0623
0.0617
0.0611
0.0605
0.0600
0.0595
0.0590
0.0585
0.0580
.UUUo
.0006
.0006
.0006
.0006
.0006
.0006
.0006
.0006
.0006
.0006
.0005
.0005
.0005
.0005
.0005
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0.0328
0.0313
0.0299
0.0285
0.0272
0.0259
0.0247
0.0236
0.0225
0.0215
0.0205
0.0196
0.0187
0.0178
0.0170
.0015
.0014
.0014
.0013
.0013
.0012
,0011
.0011
.0010
.0010
.0009
.0009
.0009
.0008
.0008
17.2
17.0
16. 8
16.6
16.4
16,2
16 .0
15.8
15.6
15.4
15.2
0.0949
0.0940
0.0931
0.0922
0.0914
0.0906
0.0898
0.0890
0.0882
0.0874
0.0866
.0009
.0009
.0009
.0009
.0008
.0008
.0008
.0008
.0008
.0008
.0008
0008
6.2
6.0
5.8
5. 6
5. 4
5. 2
5.0
4.8
4. 6
4.4
4. 2
0.0575
0.0570
0.0565
0.0560
0.0555
0.0550
0.0545
0.0540
0.0535
0.0530
0.0525
.UOUo
.0005
.0005
.0005
.0005
.0005
.0005
.0005
.0005
.0005
.0005
OOO 1 !
21
22
23
24
25
26
27
28
29
30
31
0.0162
0.0154
0.0147
0.0140
0.0133
0.0127
0.0121
0.0115
0.0110
0.0105
0.0100
.0008
.0007
.0007
.0007
.0006
.0006
.0006
.0005
.0005
.0005
15.0
0.0858
4.0
0.0520
JVC,
/if?
too
f
tftf-
\ w
kt
V
M