an evaporator 11 includes a housing 12 having sidewalls 13 , 14 , a front sidewall 5 , a rear sidewall 16 and a top wall 17 . supporting the housing 12 are a plurality of rollers 18 . a power cord 19 for connection in a suitable household outlet ( not shown ) extends out of the rear sidewall 16 . included in the front sidewall 15 is an upper inlet portion 21 defining a plurality of inlet openings 22 . also included in the front sidewall 15 is a door 23 . the rear sidewall 16 includes an outlet portion 25 that defines a plurality of outlet openings 26 . as shown in fig4 and 5 , the outlet portion 25 of the rear sidewall 16 supports in a vertically stacked arrangement an upper trough vessel 31 and a lower trough vessel 32 . retained by the upper trough 31 is an upper wick cartridge 34 having a source portion 35 disposed in the trough 31 and an evaporative portion 36 projecting upwardly therefrom . similarly , the lower trough 32 retains a lower wick cartridge 38 having a source portion 39 within the trough 32 and an evaporative portion 41 projecting upwardly therefrom . a blower fan 43 is supported within the housing 12 between the inlet 21 and the outlet 25 . rotatably coupled to the fan 43 is an electrical motor 44 connected to a conventional electrical control section 45 retained in an upper front portion of the housing 12 . when energized , the motor 44 produces rotation of the fan 43 to produce airflow between inlet 21 and the outlet 25 in a path that includes the upper evaporative portion 36 of the upper wick cartridge 34 and the lower evaporative portion 41 of the lower wick cartridge 38 . also retained in the upper portion of the housing 12 behind the electrical control section 45 is an open tray 47 that is disposed above the upper wick cartridge 34 . covering the tray 47 is a lid portion 48 of the top wall 17 . the lid 48 can be opened as shown in fig4 to provide access to the tray 47 . retained in a lower portion of the housing 12 below the lower trough 32 is a removable container 51 that defines a reservoir 52 for a supply of liquid such as water . formed on opposite sidewalls of the container 51 are aligned support shoulders 53 , 54 that slope downwardly toward a rear wall 56 . a vertical ridge 57 projects inwardly from the rear wall 56 and defines an actuator surface 58 . removably supported on the support shoulders 53 , 54 is a tank 61 that slopes downwardly therewith . as shown most clearly in fig6 the tank 61 has a bottom wall 62 that defines a valve recess 63 and a pump recess 64 . formed in the bottom wall 62 within the valve recess 63 is an externally threaded spout 66 that can be used to fill the tank 61 with liquid . a cap 67 for the spout 66 retains a conventional check valve 68 having an outwardly projecting actuator stem 69 . with the tank 61 in a fully inserted position on the container 51 as shown in fig4 the vertical ridge 57 on the rear wall 56 is accommodated by the valve recess 63 and the actuator stem 69 forcibly engages the actuator surface 58 . a handle 71 extends between outer sidewall portions of the tank 61 . access to the removable container 51 and the removable tank 61 is provided with the door 23 in an open position as shown in fig4 . a pump assembly 73 is retained in the lower portion of the housing 12 below the upper and lower troughs 31 , 32 . pivotably supporting the pump assembly 73 from the rear wall 16 of the housing 12 is a pivot pin 75 . the pump assembly 73 includes a liquid pump 76 disposed near the bottom of the container 51 and a conventional float mechanism 77 adapted to move upwardly and downwardly in response to changes in the level of the liquid within the reservoir 52 . operably coupled to the float mechanism 77 is an electrical on / off switch 78 connected between the electrical motor 44 and the electrical control section 45 . the pump assembly 73 is accommodated by the pump recess 64 in the tank 61 . as shown in fig5 a first feed tube 81 has one end attached to an outlet of the pump 76 and an opposite end opening into a collection vessel 82 in the upper portion of the housing 12 adjacent to the tray 47 . liquid fed into the collection vessel 82 drains through an outlet tube 83 in the bottom thereof into a feed chamber 80 . providing liquid communication between outlet tube 83 in the bottom of the collection vessel 82 and the upper trough is a second feed tube 84 . a drain tube 85 has a bottom end disposed in the lower trough 32 and an upper end attached to an upper overflow tube 86 that projects upwardly into the upper trough 31 . similarly , a discharge tube 88 has a bottom end disposed in the container 51 and an upper end attached to a lower overflow tube 89 projecting upwardly into the lower trough 32 . the outlet portion 25 of the rear sidewall 16 , the upper and lower troughs 31 , 32 and the upper and lower wick cartridges 34 , 38 retained thereby constitute a integral unit 91 that is pivotably supported by the housing 12 . as shown in fig7 and 8 , each side of the unit 91 has outwardly projecting spindles 92 that are received by bayonet type openings 93 formed in straddling portions 94 of the housing 12 . each of the openings 93 includes a vertical slot portion 95 and a horizontal slot portion 96 . the spindles 92 are pivotably retained at the bottom of the vertical slots 95 and permit pivotal movement of the unit 91 between a closed position shown in fig4 and an open position shown in fig3 . resilient tabs 97 projecting outwardly from the sides of the unit 91 engage the edges of the housing portions 94 to retain the unit 91 in its open position shown in fig3 . however , by moving the spindles 92 upwardly in the vertical slots 95 to provide access to the horizontal slots 96 and forcing the resilient tabs 97 by the housing portions 94 the unit 91 can be fully separated from the housing 12 . prior to use of the evaporator 11 , the tank 61 is removed through the opened door 23 and filled with liquid through the filling spout 66 after removal of the cap 67 . after replacement of the cap 67 on the spout 66 , the tank 61 is inserted through the opened door 23 onto the support shoulders 53 , 54 on the container 51 . upon full insertion of the tank 61 , the actuator stem 69 forcibly engages the actuator surface 58 to open the valve 68 and produce discharge of the liquid within the tank 61 into the container 51 . a given minimum liquid level within the container 51 moves the float mechanism 77 upwardly to close the switch 78 and permit energization of the fan motor 44 and the pump 76 in response to selective manipulation of the electrical control section 45 . energization of the pump 76 produces liquid flow out of the reservoir 52 through the first feed tube 81 , the collection vessel 82 and the second feed tube 84 into the upper trough 31 . that liquid flow establishes a predetermined liquid volume in the upper trough 31 as determined by the height of the open upper end of the upper overflow tube 86 . additional liquid flow into the upper trough 31 is fed by gravity through the drain tube 85 into the lower trough 32 to establish therein a given liquid volume determined by the open upper end of the lower overflow tube 89 . additional liquid flow into the lower trough 32 is returned by gravity through the overflow tube 89 and the discharge tube 88 into the reservoir 52 . water retained in the upper trough 31 saturates the source portion 35 of the upper wick cartridge 34 and capillary action produces migration of that liquid into the upper evaporative portion 36 . similarly , liquid retained in the lower trough 32 saturates the source portion 39 of the lower wick cartridge 38 and that liquid flows upwardly into the lower evaporative portion 41 . air flow provided by the rotating fan 43 moves air in through the inlet 21 , the evaporative portions 36 , 41 of respectively , the wick cartridges 34 , 38 and the outlet 25 . the liquid evaporated from the wick cartridges 34 , 38 is transferred by the moving air into the surrounding environment to cause humidification thereof . if environmental cooling in addition to humidification is desired , the tray 47 can be filled with ice through the opened lid 48 . cold liquid produced by melting of the ice in the tray 47 is fed by gravity through a drain opening 101 in the tray 47 into a transfer trough 102 disposed directly above the upper wick cartridge 34 . drain slots 103 in the bottom of the transfer trough 102 allow gravity induced flow of cooling liquid through the drain slots 103 into the upper evaporative portion 36 of the upper wick cartridge 34 . accordingly , air flow produced by the fan 43 through the upper evaporative portion 36 of the upper wick cartridge 34 is both cooled and humidified . for purposes of cleaning , it is sometimes desirable to remove the container 51 from the housing 12 . in that event , the tank 61 is removed through the opened door 23 , and the pump assembly 73 is pivoted into an upright position above the rearwall 56 of the container 51 as shown by dashed lines in fig5 . the container 51 then can be removed through the opened door 23 . obviously , many modifications and variations of the present invention are possible in light of the above teachings . it is to be understood , therefore , that the invention can be practiced otherwise than as specifically described .