Rollo's Museum

came to his father, who was sitting

, as we can the water, and then perh

ents with the air as i

d Rollo; "I d

; but then we can see its effects,

we can't build a dam, and make it

and no water on the other; and then, by opening a hole in the board, the water spouted through; but we cannot very well ge

do that, sir

above us. Whereas, in respect to water, you had one little stream before you, which you could manage just as you pleased. If you were down at

llo, "the water wo

ce, from this room, then bore a hole through the wall, the weight of the air outside would crowd a portion of it throug

ould try it,

d his father, "in this room; or-no

where Rollo and his father were sitting. The other door opened into the back part of

r a moment, then the pressure of the air outside would force a j

get the air ou

ick. The door will carry with it a part of the air that was in the closet, and then the outside air w

ut I can put my hand

d be to hold a lamp opposite to the ke

key-hole, and pretty near to it, and then he asked Nathan to shut the other door suddenly. Nathan, who was standing all ready by the ot

her, "you need not be qu

ather, it succee

father; "but Nathan need not have

ve out all the a

how to do it,"

the door wide, and then explained to the boys, that the beginning of th

by the movement of the door, can pass directly round the edge, back into the closet again. It is only when the door is

d the latch so as to prevent its snapping against the catch, and then pushed it suddenl

-hole, and watch the flame, while I shut

the lamp was driven into the room every time the door was shut; proving that, every time

-hole," said Rollo, "an

reat many little crevices all around t

top those up t

r-tight. For, if the crevices could all be stopped exac

said

ttle channels that the sap flowed in when the woo

ry intently at the table; and he asked him what he was

se-grained kind of wood. If it was summer, and you could dig down and get a small piece o

did not just then think of any experiment, but that, if Rollo and Nathan would come and sit down by the fire, he would give them some information on the subje

y respects muc

"just like water, only t

ecessary to understand what I say. It is entirely irregular for a pupil, instead of li

this, but Rollo looked rather as

erence between them. Water is not

ing of compressib

ssed together, so as to take up less room than they did before. Sponge is compressible.

was," said Nathan

way. If you have a tumbler half full of water, and press a ball down into it, you could not crowd the water into any smaller

was just big enough to fit the tumbler all

father, "you could no

ery strong man

if a ball were to be put in at the top, just large enough to fit the tumbler exactly, and if a strong man were to cr

mbler would bre

nswer only for a supposition; but for a real exper

cylinder?"

is at the top, would be a cylinder. Now, if there was a cylinder of iron

piston?"

made to fit perfectly, and then it is oiled, so as to go up and down without much friction, that is, hard rubbing. There is a so

ch it occupied before. That is, if the cylinder was full of air when he put the piston in, perhaps he could get the piston down half way to the bottom. Then the air would be twice as dense as it was before; that

does not begin the condensation when the piston begins to descend. The air is

t condensed?

ed a hole through the board in the bot

, "we pulled the plug ou

father, "the wa

said

it?" said

y, and pressed down upon it, and

the deeper the water, the m

Rollo, "and the f

down by the load of such

ir," sa

is pressed down by the load of all that is above us. We are, in fact, down at t

vy?" sai

y indeed," sa

pretty light,

her, "but then the col

gh?" sa

owards the top; so it is not as heavy, by any means, as a column of air

nner and thinner toward

ch is near the top, has not as much l

op," said Rollo, "has none

plied hi

thin is i

ows," said

dy at all?"

ast I do not; and I don't

, then, how high

ve they have ascertained how great the pressure of the air is here at the surface of the earth,

must it be?"

forty miles," said Roll

r of thirty or forty miles. That is, the air around presses about as heavily, and would force a jet of air through a ho

mother; but Nathan found it rather hard to understand them all, a

en't you almost done

ave told you enough for this time

n remember it quite

load of all the air above; that, being so pressed, the lower air is condensed,-so that we live in the midst of air that is pressed down, and condensed, by the load of all that is above it; and that, conse

tle too much for me to

they were laughing at. His father told him that he could not expect him to remembe

boy, who went about the yard with a little dog upon one of his shoulders

STI

uld be forced into the closet? How were they to make this effect visible? Did the experiment succeed? Suppose the key-hole had been stopped up; where would the air have been forced in? Suppose all the crevices had been closed. Is

to co