December.] hot- house of shutters. 185 



DECEMBER. 



The uncertainty of the weather in this month requires 

 the operator to be constantly on guard, to ward off danger, 

 either from frost, snow, or cutting winds. The temperature 

 observed last month must be continued, but not exceeded, 

 which would cause premature vegetation, of which the result 

 and effects have already been observed. Always kindle the 

 fires in time, to prevent the heat from being lower than what 

 has been mentioned, lest a severe frost should take place, as 

 then a considerable lapse ensues before the fire has any effect; 

 and if the wind blows high, the result might be injurious, 

 unless the house be very close. 



of shutters 



The benefit of these in severe weather is of material 

 service, for the preservation of an even temperature in the 

 house during the night, when changes are not observed ; but 

 they ought never to remain on through the day, when the fire 

 can be properly attended to. If the front and the lowest sash 

 of the roof are covered with those, it is generally sufficient. 

 They should be made of three-quarter inch boards, closely 

 grooved together, having a cross-bar in the centre, and one at 

 each end and each side, which will make them substantial. 

 If they are frequently painted with care, they will last many 

 years. Snow ought not to be allowed to lay on these while 

 they are on the glass, for reasons that we have assigned. 

 See January and February. 



Some adopt double panes of glass to supersede the use of 

 shutters, which they think are attended with considerable 

 labour (at the most only fifteen minutes a day, while in use.) 



The sash frame is made a little deeper, s > as to allow half 

 an inch between the panes of glass. The one is glazed from 

 the out and the other from the inside. It appears to answer 

 the purpose tolerably well, but the glass must be both fine 

 and even on the surface, lest a lens should be produced, 

 which would scourge the plants. We are almost confident 

 that we have seen this effect in some instances. There must 

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