A Guide To The Scientific Knowledge Of Things Familiar - novelonlinefull.com
You’re read light novel A Guide To The Scientific Knowledge Of Things Familiar Part 27 online at NovelOnlineFull.com. Please use the follow button to get notification about the latest chapter next time when you visit NovelOnlineFull.com. Use F11 button to read novel in full-screen(PC only). Drop by anytime you want to read free – fast – latest novel. It’s great if you could leave a comment, share your opinion about the new chapters, new novel with others on the internet. We’ll do our best to bring you the finest, latest novel everyday. Enjoy
Any liquid which boils at a _lower_ degree can be made to boil if immersed in a liquid which boils at a higher degree. Thus a _cup of ether_ can be made to boil in a saucepan of _water_. A _cup of water_ in a saucepan of _brine or syrup_. But a _cup of water_ will _not_ boil if immersed in _ether_; nor a _cup of syrup_ in _water_.
Q. _Why are CLOUDS HIGHER on a FINE DAY?_
A. 1st--Because the _air_ (expanded by heat) _drives them higher up_: and
2ndly--The _clouds themselves are lighter_, and therefore _more buoyant_.
Q. _Why are the CLOUDS LIGHTER on a FINE DAY?_
A. Because their mists are either _absorbed by the dry air_, or _vapourized_ by the hot sun.
Q. _Why is a CUP PUT topsy-turvy into a FRUIT-PIE?_
A. Its princ.i.p.al use is to _hold the crust up_, and _prevent it from sinking_, when the cooked fruit gives away under it.
Q. _Does not the cup PREVENT the FRUIT of the pie from BOILING OVER?_
A. No, by no means; it would rather tend to _make it boil over_, than otherwise.
Q. _Why would the cup tend rather to MAKE the FRUIT BOIL OVER?_
A. As soon as the pie is put into the oven, the _air_ in the cup will _begin to expand_, and drive every particle of juice from under it; the pie dish, therefore, will have a cup-full _less room_ to hold its fruit, than if the cup were _taken out_.
Q. _If the juice is driven OUT of the cup, why is the CUP always FULL of JUICE, when the pie is cut up?_
A. Immediately the pie is drawn, the _air_ in the cup begins to _condense again_, and _occupy a smaller s.p.a.ce_; in consequence of which, there is no longer _enough air to fill the cup_, and so _juice_ rushes in _to fill up the deficiency_.
Q. _Why does JUICE rush into the cup, because the cup is NOT FULL of AIR?_
A. As the external air _presses upon the surface of the juice_, it rushes into the cup _un.o.bstructed_; as mercury rises through the tube of a barometer through similar pressure.
CHAPTER X.
EXPANSION FROM HEAT.
_(Continued.)_
Q. _Does heat expand every thing ELSE BESIDES air and water?_
A. Yes; _every_ thing (that man is acquainted with) is expanded by heat.
Q. _Why does a COOPER make his HOOPS RED-HOT, when he puts them on a tub?_
A. 1st--As _iron expands by heat_, the hoops will be _larger_ when they are red-hot; and will, therefore, _fit more easily on the tub_: and
2ndly--As _iron contracts by cold_, the hoops will _shrink_ as they cool down, and _girt the tub with a tighter grasp_.
Q. _Why does a WHEELWRIGHT make his hoops RED-HOT, which he fixes on the NAVE of a WHEEL?_
A. 1st--That they may _fit on more easily_: and
2ndly--That they may _girt the nave more tightly_.
Q. _Why will the wheelwright's HOOP FIT the nave MORE EASILY, because they are made RED-HOT?_
A. As _iron expands by heat_, the hoops will be _larger_ when they are hot; and (being larger) will go on the nave more _easily_.
Q. _Why will the HOOPS, which have been PUT ON HOT, girt the nave more FIRMLY?_
A. As _iron contracts by cold_, the hoops will _shrink as they cool down_; and, therefore, _girt the nave with a tighter grasp_.
Q. _Why does a farrier put the HORSE-SHOE on HOT?_
A. That it may _stick the closer_, when it has contracted by cold.
Q. _Why does a STOVE make a CRACKING NOISE, when a fire is very hot?_
A. The iron stove _expands by heat_, and (as it swells) the parts rub both _against each other_, and _against the bricks around_, driving them further off; and this produces a _cracking_ noise.
Q. _Why does a STOVE make a similar CRACKING NOISE, when a large FIRE is TAKEN DOWN?_
A. The iron stove _contracts again_, as soon as the fire is removed; and (as it shrinks into a smaller s.p.a.ce) the parts _rub against each other again_, and the _bricks are again disturbed_; and this produces a cracking noise.
Q. _Why does the PLASTER round a STOVE CRACK and fall away?_
A. When the fire is lighted, _the iron-work_ (which expands more than the brick-work and plaster) _pushes away the bricks and plaster_: but when the fire is put out, the metal _shrinks_ again, and _leaves the "setting" behind_.
Q. _Why does the PLASTER FALL AWAY?_
