space produce the actual sound from this tendency of there to rush into empty spaces is also one of the principal causes a storm the air around us exerts a pressure on every square inch of surface exposed to it in the weather forecasting stations sensitive instruments show that this atmospheric pressure varies occasionally because of local weather conditions when the pressure in one locality becomes temporarily lower the weatherman knows that winds will blow as great masses of their rush in to fill up the space special maps are made to chart these variations in pressure to help trace the paths of wind which may carry rain or snow these low pressure areas are created naturally we all see a loss grayson's of the action of artificially produced low pressures in our daily lives when we drink through a straw for instance suc creates a partial vacuum on so that the air pressure in the straw and in imo is left on the normal lap pressure on the surface of the liquid in the bottle this difference in pressure forces the liquid up to fill the empty space inside of  sprawl by drawing in air the smoker reduces the pressure inside his the gong the normal air pressure on the outside forces the smoke through the cigar and into his mouth when the discover suction cup is flatten the area for stowe when the cup springs back to shape it forms a hollow space with very little air in it the normal pressure on the outside of the cup holds it against the wall with considerable f in an airplane and the rapid movement of the wing through the air causes differences in pressure they keep up the wing and the angle at which it is set causes the air rushing past it to count against the lower surface increasing the pressure under the wing for the same reason they air rushing past the upper surface leaves a gap and lowers the pressure on top of the wing the difference between the high pressure under and the low pressure above forces the plane upwards scientists say that most of the lifted due to the extremely low pressure or partial back your own on the upper surface although even the most advanced science has not been able to produce a perfect vacuum or space in which there is nothing at all done next to nothing this we call a partial vacuum can be produced and controlled we can create a partial vacuum if we first fill a glass tube with mercury to drive up the air when the tube is up ended the mercury falls living in almost empty space at the top the mercury remaining in the tube is held in place by the weight of  pressing on the surface of the macquarie in the days if normal air pressure in one side of a u shape to it increased by pushing a piston down the pressure will force the american way up in the other arm when we different strain in this heavy duty vacuum cleaner large fans lower the air pressure in a hose connected to the furnace normal air pressure rushing down the chimney carries with it the sort i'm direct and forces them through the hose into a huge bag this same vacuum force is put to work in modern city post offices mail is placed in containers made to fit snugly into large pneumatic tubes a partial vacuum ahead of the container permits normal air pressure behind the containers to force it through miles up to being at lightning speed so the problem of empty space has greatly increase the efficiency of uncle sam's postal department and has made possible the delivery of letters and parcels in less time than ever before the latest successful application of pressure vacuum to radios work is in the automobile automotive engineers knew that the comfort and safety of the modern motor car could be increased by making it easier and more convenient to hit gears the fundamental operation of the gear shift lever is simple when the knob on the shift lever is moved in one direction the bottom of the lever moves in the opposite direction the movement of the bottom of the lever causes the right gears inside the transmission case to mesh with other gears to drive the car with the right speed no suppose the gear shift l off the floor and move to the most accessible convenient position right alongside the steering wheel the method of shifting is the same although the lever as been turned on its side there has been no change in the shifting movement the next thing is to connect the shift lever to the gears themselves along rod connected to the bottom of the shift lever will transmit movement to a crank at the other end of the steering wheel proles and another rod and crank will carry the movement back to the gears know when the hip lever is moved the system of rods goes into action and felix the required gear but this is only half the job after the gear has been selected by the up and down movement of the hip lever it has to be shifted into position so that it will make another rod is needed to do this happen the job of shifting gears and to make the system more compact the second rod can be made possible so that it will slip right over the rod already in place to separate its motion from the back and forth movement of the inner rod this outer rod or tube can carry a twisting movement instead of a push pull the twisting motion of the other rod will turn another crank at the bottom of the steering poles and this motion can be passed on to the lever which does the actual shifting with this arrangement any movement of the gear shift lever carries a corresponding movement to the transmission this is simple the selection of gears is almost effortless but the actual shifting takes the certain amount of work out a lever to feet long and moving ten inches changes gears with ease but a long lever on the steering post is inconvenient shorter gear shifting lever is more convenient but since the movement is shorter more than forty is required especially in cold weather latest development is to let the normal air pressure of the air around us do the actual work of shifting the gears in an automobile engine moving pistons act like pumps creating a partial vacuum to draw fuel into the cylinders up thank you  chamber connected to the intake make use of this radius pressure i'm moveable plunger divides the chamber into two separate sections no when air is drawn out of one section of the chamber lowering the pressure the norm pressure in the other section will drive the plunger exerting force on every square inch of a circus by reversing the operation the plunger is forced back in the opposite direction our sliding valve controls the action with the slightest movement of the hip lever the plunger is connected so that it transmits force directly to the lever that engages and disengage the gears with so little effort required to shift the gears and with a minimum of movement the gear shift control lever can be brought down to a still more convenient size the power to back you implement the shorter lever moving a shorter distance the hand of merely applies the power and back you own does eighty percent of the work of gear shifting again and generic design has moved forward driving has been made easier for everyone the prone out vacuum shifting the gears makes fingertip control possible with a minimum of effort the driver is able to keep control of the car at all times and to shift gears at will according to actual driving ne flip of the finger and in second gear steep grades are taken with the car in perfect control no muscular effort is required there's just enough resistance to let the driver sense the feel and timing of the gear this modern easy shifting another impossible for safety has been made on the newest automobile the emergency brake has been moved up out of the way and conveniently located on the back there is greater convenience for today's motorists than ever before taking the control levers from the floor has made more room and more comfort for the driver and front seat passenger because we can now enter and leave the car on the side away from