164 MANUAL OF GARDENING 
A very good temporary protection may be given to tender 
plants by using four panes of glass, as explained in Fig. 193, the 
two inner panes being held together at the top by a block of 
wood through which four nails are driven. Plants are more 
likely to burn in these glass frames than in the hand-boxes, and 
such frames are not so well adapted to the protection of plants 
in very early spring; but they are often 
useful for special purposes. 
In all forcing-hills, as in coldframes and 
hotbeds, it is exceedingly important that 
the plants receive plenty of air on bright 
days. Plants that are kept too close be- 
come weak or “drawn,”’ and lose the ability 
to withstand changes of weather when the protection is re- 
moved. Even though the wind is cold and raw, the plants 
inside the frames ordinarily will not suffer if the glass is 
taken off when the sun is shining. 
193. Glass forcing-hill. 
Coldframes. 
A coldframe is nothing more than an enlarged hand-box; 
that is, instead of protecting but a single plant or a single hill 
with a single pane of glass, the frame is covered with sash, and 
is large enough to accommodate many plants. 
There are three general purposes for which a coldframe is 
used: For the starting of plants early in spring; for receiving 
partially hardened plants that have been started earlier in 
hotbeds and forcing-houses; for wintering young cabbages, 
lettuce, and other hardy plants that are sown in the fall. 
Coldframes are ordinarily placed near the buildings, and the 
plants are transplanted into the field when settled weather 
comes. Sometimes, however, they are made directly in the 
field where the plants are to remain, and the frames, and not 
the plants, are removed. When used for this latter purpose, 
the frames are made very cheap by running two rows of parallel 
