GLASS STRUCTURES. 71 



The heat from a flue is very dry, and much more water is 

 required when hotbeds are heated in this way than when manure 

 is used as the source of heat. 



A Greenhouse Hotbed. — A greenhouse may be heated by 

 manure or a combination of manure and other artificial heat> 

 In the following lines and illustrations is given the plan of what 

 may be called a greenhouse hotbed which has been in very suc- 

 cessful operation at the Minnesota Agriculaural School. The de- 

 scription is from an article on the subject by R. S. Mackintosh, of 

 the Division of Horticulture. 



''There are disadvantages in hotbeds, as, for instance, the 

 transplanting, ventilating, watering, etc., must be done from the 

 outside even in severe weather, while in a house like the one 



Figure 28. — Plan and ele\ ation of hotbed greenhouse. 



shown in the figure these operations can be carried on easily. 

 The house is simply a hotbed built so as to allow a person to gc 



