Page 22
CO M P R E S S IB IL IT Y OF A IR
1 A double pressure-pump made by John Cuthbertson, in which the two glass
cylinders and a brass cylinder, which are screwed between brass plates, have
been given taps which fit on to the pump. With this also a brass sphere, which
fits on to the pressure-pump, and on which the cylinders can be screwed, to
allow the air in this sphere first to be highly compressed, and next to allow
this compressed air to go into the cylinder which is screwed on to the sphere.
2 A brass cylinder, with its pressure-syringe and several jets, which will make
several fountains by compression of air in the cylinder, ’s Gravesande, LXXI,
fig. 4.
3 The fountain of Hero.
f 4 A long, compound glass mercury tube, united by means of iron tubes in the
shape of a syphon, to show that the space taken up by air decreases in the
same proportion in which the pressure force increases.
5 An apparatus to show that the elasticity of air decreases in proportion to the
decrease in density, consisting of two small disks connected to each other, on
which stand two long cylinders of equal capacity, and in these, barometer
tubes are fixed. After the evacuation of one cylinder, the air from the other,
when the tap is opened, divides itself equally in both, and is therefore rarefied
by half; then the mercury column will descend to half of its previous height.
Page 23
W E IG H T AND PRESSURE OF A IR
i A glass sphere o f ... inches diameter, with a tap, to weigh air.
t 2 A similar sphere of ... inches diameter.
t 3 A cord-bound glass cone, on which to put one’s hand when one wants to feel
the pressure of air on the hand caused by the rarefaction of air.
f 4 A similar, with which to break a flat glass by the pressure of air.
5 A similar, with which to break a bladder by the pressure of air.
6 A small disk on which is placed a small bell-jar with a ring, in a cylinder, on
which there is a cover with a sliding-rod and hook that fits in the ring of the
small bell-jar; to demonstrate that a smaller bell-jar is secured under a larger
one when one allows the air to enter the larger bell-jar quickly, and again is
loosened when the air is again rarefied.
f 7 small syringe to which is screwed a lead weight, and which can be suspended
in rarefied air by means of a hook, to show the resistance one notices
when one raises the plunger, caused by the pressure of the air.
8 Two similar glass bell-jars on two small disks connected together, to demonstrate
the fastening of a bell-jar when half its air goes into another bell-jar.
Page 24
PRESSURE OF A IR
j- i An apparatus to demonstrate that the pressure sideways, upwards and in all
directions is equal to the vertical, consisting of three equal cylindrical glass
vessels on which are stretched membranes, and which can be positioned in
every direction to a bent tube, which is screwed to the table of an air-pump.
f 2 A bottle in which a hole has been drilled in the side.
f 3 A barometer tube with a hole drilled in the side.
| 4 A Wijnsteefcer’s pump.
| 5 A portable watering can.
| 6 A glass cylinder of... inches with a tap and a flat ground edge, to demonstrate
the holding up of water in glasses with wide mouths by upwards pressure of
air.
7 The intermittent fountain of Sturmins.
8 The same completely blown in glass.
9 A so-called magic spout.
| 10 A disk with a tap, to which can be screwed a glass tube on which can be
placed a long cylinder, to make a waterfall in rarefied air by means of air
pressure.
Page 25
TH E POWER OF TH E PRESSURE OF A IR
i Two flat polished brass plates, with rings.
f 2 Two half brass spheres of 3 inches diameter.
3 Two half brass spheres of inches diameter
f 4 A large glass bell-jar placed on a brass ring, and with a coverplate and sliding
rod to let disconnect from each other, in strongly evacuated air, two brass
spheres [hemi-spheres] of about 500 lbs. pulling power, which are almost
completely evacuated, and to allow the same to be pressed together when the
air is let in.
f 5 A tripod with a hook and scale, for experimenting with these spheres.
t 6 A glass, in the bottom of which is fixed an oak branch three inches long, to
demonstrate the squeezing of the air through this wood when the air above
the water, with which the glass is partially filled, is rarefied.
t 7 A small wooden trough, on a wide glass bell-jar, to demonstrate the squeezing
of mercury through wood by the pressure of air.
Page 26
b a r o m e t e r
1 A barometer under a glass dome, closed at the top by a tap, to show
that the mercury in the barometer is held up by air pressure.
2 A bent glass tube that is screwed on the tap of this cover, and of which the
lower end is placed in a glass with mercury, to show that the mercury will rise
in this tube while the air in the same is rarefied.
t 3 A barometer tube, that is closed at the top by a bladder, to demonstrate the
descent of the mercury when the bladder is pierced.
4 Four shortened barometers or mercury tubes in the shape of syphons on small
bases, to place under air-receivers to indicate the degree of evacuation.
T 5 A shortened barometer tube on a small board.
t 6 Four barometer tubes standing in the same mercury trough to show what
width the barometer tube should have.