[Verse: "The wind bloweth where it listeth, and thou hearest the sound thereof, but canst not tell whence it cometh, and whither it goeth: so is every one that is born of the Spirit."--JOHN II., III.] 652. _How high will atmospheric pressure raise water in the bore of a pump?_ It will raise water to an elevation of _thirty feet_ above its level. 653. _Why will it raise water to an elevation of thirty-feet?_ Because a column of water of _thirty feet high_, nearly balances the weight of _a column of air_ of equal surface, _extending to the whole height of the atmosphere_. When, therefore, water is elevated to the height of thirty feet, the power of the pump is enfeebled, as the air and the water _balance each other_. 654. _How is water raised to a greater elevation when it is required?_ By mechanical contrivances, by which the water is _forced_ to a greater elevation. 655. _Why does water run through the bent tube called a syphon?_ Because the atmospheric pressure upon the water on _the outside of the syphon_ forces it into the tube as fast as the syphon empties itself through its longer arm. 656. _Why does water run through the longer arm of the syphon?_ Because the weight of the water in the longer arm of the syphon _is greater than that in the shorter_; therefore it runs out by its own gravity. And, as in running out, it creates a tendency towards a _vacuum_, the pressure of the outer air comes into operation, and forces the water through the tube. 657. _Why does water issue from the earth in springs?_ Some springs are caused by _natural syphons_ formed in the fissures of rocks, which, communicating with bodies of water, are continually filled by atmospheric pressure, and therefore convey streams of water to the point where they are set free. [Verse: "Ascribe ye strength unto God: his excellency is over Israel, and his strength is in the clouds."--PSALM LVIII.] 658. _Why, if a wine glass is filled with water, and a card laid upon it, and the whole inverted, will the water remain in the glass?_ Because the pressure of the atmosphere upon the surface of the card counteracts the weight of the water. 659. _What has the card to do with the experiment?_ It forms _a base_ upon which the water may rest, while the glass is being inverted; and it prevents the air from acting upon the _fluidity_ of the water, and forcing it out of the glass. 660. _Why will not beer run out of the tap of a cask until a spile has been driven in at the top?_ Because the pressure of the air upon the opening of the tap counteracts the weight of the beer. But when the spile is driven in, the air enters at the top, _and counteracts its own pressure at the bottom_. 661. _Why does a cup in a pie become filled with juice?_