CONSTRUCTION OF HOTBEDS 
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should give all the protection needed by plants ordinarily 
grown in frames. (2) The labor in the management of 
the frames is reduced, because there are no mats to be 
handled morning and evening. (3) The plants receive 
the light during the entire day, because there are no mats 
at any time to obstruct it. (4) A growing temperature 
is reached earlier in the day, and is maintained longer, 
unless there is little or no sunshine. 
Disadvantages that may be mentioned are: (1) Double- 
glass sash are much heavier to handle, and this is one 
of the greatest objections raised by men who handle sash 
by the hundreds. (2) They cost about one-third more. 
(3) On account of the accumulation and retention of 
moisture between the two layers of glass, it is thought 
that the sash will not be so durable as single-glass sash. 
(4) The two layers of glass and the accumulation of dirt 
and moisture between the panes reduce the amount of 
light entering the frames, and in consequence produce 
weaker plants. This new type of sash can be used to 
advantage for many purposes, although the single-glass 
type will doubtless continue to be popular in sections 
where hotbeds are used extensively. Oiled paper and 
special waterproof cloth are substituted for glass some- 
times. Although less expensive, they lack durability and 
do not generally give as satisfactory results as glass sash. 
158. Manure and its preparation. — Practically all 
manure hotbeds are made with horse manure. Poultry 
and sheep manures are also desirable, although they are 
too valuable in fertilizing garden crops to be used for this 
purpose. Spent hops from breweries, and forest leaves, 
may also be worked into the hotbed manure, which 
should be fresh and not too compact nor too loose. If 
it is composed almost entirely of the solid excrements 
of the horse, with whatever urine it has absorbed, it may 
fail to heat, or the fermentation may be too violent and 
of too short duration. Two parts of excrement to one 
