. The Boston school compendium of natural and experimental philosophy .. . piston is forced through the tube into the reservoir or air vessel R, where it compresses the air above it. The air, by its elasticity, forces the water oui through the jet J in a continued stream and with great force. It is on this principle that fire engines are constructed. Sometimes a pipe with a valve in it is substituted for the air vessel; the water is then thrown out in a continued stream, but not with so much force. 262. Wind is a current of air put in * The handle of a common pump 13 a lever of the fi
. The Boston school compendium of natural and experimental philosophy .. . piston is forced through the tube into the reservoir or air vessel R, where it compresses the air above it. The air, by its elasticity, forces the water oui through the jet J in a continued stream and with great force. It is on this principle that fire engines are constructed. Sometimes a pipe with a valve in it is substituted for the air vessel; the water is then thrown out in a continued stream, but not with so much force. 262. Wind is a current of air put in * The handle of a common pump 13 a lever of the first kind, the shorterarm of which is connected with the piston.* When the handle is pressed down, thepiston The valves, and the parts which contain them, are, in commonlanguage, called boxes. t There are two ways in which the motion of the air may be explained. It maybe considered as an absolute motion of the air, ratified by heat and condensed bycold—or ii may be only an apparent motion, caused by the superior velocity ofthe earth in its daily revolution. B. Which of the mechanical powers i3 the handle of the pump? 260. How highcan water be raised by the common pump . Why J 261. How does the forcingpump differ from the common pump; What figure represents the forcing pump IExplain it. 262. What is wind ! In what two ways may the motion of theair be explained? 96 NATURAL PHILOSOPHY. Explanation. When any portion of the atmosphere is heated, itbecomes ratified, its specific gravity is diminished, and it conse-quently rises. The adjacent portions immediately rush into itsplace to restore the equilibrium. This motion produces a cur-rent which rushes into the rarified spot from all is what we call wind. The portions north of the rarified spotrush downwards, producing a North wind; those to the south rushupwards, producing a South wind; while those to the East ,in like manner, form currents moving in opposite directions. Atthe rarified spot, agitat
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Keywords: ., bookcentury1800, bookdecade1830, booksubjectphysics, bookyear1837
