72 TRANSACTIONS OF THE 
~ No. 5, patented in 1918. The object of this machine 
is to utilize the heated air until it is thoroughly saturated 
with moisture. This is done by using air of determined 
temperature and humidity, passing over a portion of the 
article to be dried, raising the temperature, mixing it 
with fresh air to maintain its original moisture-absorbing 
capacity, and passing this mixed body of air over a second 
group of material, and so on many times until the air 
is saturated with moisture. 
No. 6, patented in 1918. The theory upon which 
the operation of this machine is based is that vegetable 
matter more readily exudes moisture under the action 
of radiant heat than of convected heat, the rapidity 
also depending upon the degree of temperature and the 
amount of air pressure. The material is dehydrated 
by so arranging the apparatus that there are intermittent 
applications of radiant heat, electric light, and moving 
air currents, at definite air pressure. 
Many other devices have been invented and many 
attempts have been made to dehydrate all kinds of food- 
stuffs. They have mostly been failures as will be seen 
by the fact that Mr. Sweet, the government expert, says 
that “fully 90 percent of the dehydrated materials pur- 
chased by the government within the last two years were 
very poor and would never have been accepted except 
for the stress of war.” 
Great success has been claimed for some of the inven- 
tions I have described, but it seems to me that there are 
two principal drawbacks to the widespread adoption of 
these machines. In the first place they are so compli- 
cated in construction that they are liable to be quite 
costly to install, and what we need today is an inexpen- 
sive machine that may be easily installed by a small 
group of producers. In the second place, although in 
actual operation these machines may produce a high 
grade product, some of them are based on theories that 
either need proof, or are not applicable to the conditions. 
There are many problems still to be solved before 
we can produce the right kind of dehydrated goods. 
Even the inventor of several of these machines admits 
that the problem is not so much one of the extraction of 
water from the tissues as it is a problem of the proper 
