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AMERICAN POMOLOGICAL SOCIETY. 
Requisites of a first-class commercial evaporator are, sufficient heat generat- 
ing capacity to heat a given volume of air entering the furnace chamber from 
200 to 300 degrees F., the volume of air necessary to keep a draught of moist- 
ure saturated air equally distributed through a given amount of fruit andi 
passing off a,t a velocity of 880 feet per minute — 20 miles per hour. 
An apparatus of 450 cubic feet of air heated to 212 degrees, containing 
fruit will carry 120 lbs. of water, 100 lbs. taken from the fruit as the air at 
62 y 2 degrees will ordinarily contain 20 lbs. of water, thus it can. be demon- 
strated in practice that a draught of 880 feet per minute at this temperature 
will extract and carry off 300 lbs. of water per hour, 1,500 lbs. in five hours, 
the time required to remove the moisture from apples. Scientists have found 
that the capacity of air to absorb moisture doubles with every 27 degrees- 
Fahrenheit increase in temperature. At 194 degrees air - will absorb ap- 
proximately 3 lbs. of water to the cubic foot; at 221 degrees, nearly 6 lbs. 
Thus it is obvious that with a given machine with properly regulated de- 
flectors and damper controlling the air entering the heating chambers and tne 
heated air escaping so as to maintain the required 200 to 300 degrees of heat 
required according to the sort of fruit or stage of evaporation with the 880 
feet draught per minute, a correct estimate can be made of the evaporating 
capacity, and further the amount of water in lbs. or gallons in a given 
amount of fruit to be evaporated and the time required for the operation. 
The evaporator thus regulated to mathematical rules has been difficult of 
mechanical attainment. More than one thousand machines have been patented 
in this country, many of them doing good work in a limited way on the farm 
or in the small orchard. 
The reliable, economic working, 10 to 20 tons capacity, commercial evapora- 
tor, is not yet a well established fact; is still a subject of serious thought 
and earnest discussion in horticultural circles. As air is not a conductor of 
heat and can only be heated by contact-impinging on a heated surface, the 
difficulty has been to devise a method of heating a large body of air and con- 
trolling the equal distribution and rapid circulation through the fruit in a 
machine of large capacity. 
On the Pacific coast, in the prune districts of Oregon and Washington, 
where sun-drying is not available, it is claimed that this has been practically 
accomplished. The enormous yield in extensive orchards of the large Fellen- 
berg [Italian] Prune necessitated the construction of wholesale devices for 
handling this product. The prune, owing to the close, texture of its skin, 
requires the low temperature of 150 to 200 degrees, and 24 to 36 hours time 
for the best results — to retain the aroma and color and change the starch into 
sugar, coagulate the pectin without cooking, properly concentrate the fruit 
juices, making a soft, pliable, raisined product alike attractive to the eye and 
the palate, a veritable confection edible out of hand or from the cuisine. This 
was the end sought and accomplished. 
The comparative cheapness of the plant, facility for producing a valuable 
and attractive commercial article at fair remuneration to the producer, at 
low cost to the consumer — one-sixth to one-tenth the freight rates of canned 
goods, green fruits or other fruit preparations, conspire to make this a leading- 
industry in the future. A list of fruits and vegetables now on the market 
thus prepared comprises apples, pears, peaches, apricots, plums, prunes, 
nectarines, figs, cherries, blackberries, grapes, green corn, peas, potatoes, 
sweet potatoes, onions, tomatoes, pumpkins, rhubarb, asparagus, hops, to- 
bacco, meats, oysters, fish and eggs, etc. 
