150 Double- Glazing. 



DOUBLE-GLAZING. 



The subject of double-glazing is attracting a good deal of attention in 

 England ; and if, in that country, the advantages of a double-glass roof are 

 so great, they will certainly be far greater in our changeable climate. 



Without entering particularly into the method of constructing glass 

 houses on this plan, it may be briefly said, that a space of from four to six 

 inches should intervene between the upper and the lower roof; and, con- 

 fined air being an excellent non-conductor, the air enclosed should be as 

 closely confined as possible. 



Only two objections seem to have been made to double-glazing ; one 

 being the additional expense, and the other the diminished light from the 

 accumulation of dirt between the sashes. This latter objection amounts 

 to nothing. The dust of a whole season would be hardly more than a scum, 

 easily cleared off in two or three hours. As to the increased expense, this 

 must, of course, be weighed against the advantages ; and these we propose 

 to consider. 



Confined air being so good a non-conductor, the double glass gives all 

 the benefits arising from the use of shutters and mats, and this without 

 intercepting the light, and without the continually-recurring trouble of put- 

 ting on and taking off, with the consequent liability to break glasses. 



Then, again, we avoid " drip," not only in itself a great nuisance, but 

 also an evidence that the atmosphere of the house is being robbed of its 

 moisture, almost invariably to the great injury of the plants. " Drip " is 

 caused by the moisture in the heated air coming into contact with the cold 

 glass, and being condensed : therefore, the warmer the glass is kept, the 

 less the condensation ; and, if the glass and the air are at the same tem- 

 perature, there is no condensation, and consequently no "drip." In the 

 hot-house and stove, where the most moisture is needed, is found the most 

 " drip ; " and, since the dearly-bought plants are generally in these houses, 

 the trouble falls just where there is the least ability to bear it. 



This subject of atmospheric moisture demands the utmost attention. 

 Plants at rest should be kept comparatively dry ; but when growing rapidly, 



