DAMPNESS OF GLASS-HOUSES. 205 



of 1826, or 1827, when I resided at ' the Cedars' at Putney, the only 

 border which my next door neighbour and myself had for growing 

 early Peas, had an east aspect. A very severe frost (10°) came over 

 that district about the 15th of May. The Peas were in full bloom on 

 my neighbour's border, as well as mine. I syringed all mine with cold 

 water. My neighbour, on witnessing the operation, said that he would 

 not kill his in that way. I saved all mine, he lost aU his. This 

 taught me a lesson which I never forgot ; and by the same means I have 

 often saved the Peach, Pear, and other fruits, as well as Gooseberries, 

 after they were a good size." It is to be remembered, however, that 

 this plan is serviceable only in the case of morning frosts of short 

 dtiration. 



In our glazed houses, we have full control over the state of 

 the atmosphere, as regards both its moisture and temperature, 

 by means familiar to every gardener; but the manner of 

 applying those means, and the causes that oppose their action, 

 deserve to be the subject of inquiry. 



It will have been seen, from what has been already stated 

 upon that subject, that in general, in warm countries, the air is 

 occasionally at least, if not permanently, filled with vapour to a 

 much greater extent than in northern latitudes*, and, as in our 

 glazed houses we cultivate exclusively the natives of warm 

 countries, it is also obvious that, as a general rule, the air of 

 such houses requires, at certain .periods, to be damper than 

 that of the external air. Those periods are when vegetation 

 is most active. On the other hand, countries nearer the equator 

 are subject to seasons of dryness, the continuance of which is 

 often much greater than any thing we know of here in the open 

 air, and consequently artificial means must also be adopted 

 to bring about, in glazed houses, that state of things at particu- 

 lar periods ; namely, those of the repose of plants. These facts 

 afford abundant proof of the necessity of regulating the 

 moisture of the atmosphere with some certainty. 



The dampness of glass-houses is easily maintained at any 

 required degree by various contrivances : such as inundating 



, * " Captain Sabine, in Ms meteorological researches between the tropics, rarely found 

 at tie hottest period of the day so great a difference as 10° between the temperature 

 of the air and the dew-point ; making the degree of saturation about "730, but most 

 frequently 6° or '850 ; and the mean saturation of the air could not have exceeded 

 •910." {Dmidl.) 



