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fact, that by their foliage they increase the invisible moisture of the atmos- 

 phere and thereby counteract the drying effect of close stoves or coal fires 

 of every description. We believe Prof Gray's opinion to be correct in rela- 

 tion to the quantity of oxygen or carbonic acid consumed or given out by 

 the leaves and flowers of plants, but he does not allude to the point on 

 which we laid the most stress. 



Suppose an ordinary sized geranium to imbibe from the soil one half-pint 

 of water per day, by its roots, it must give out one half-pint of moisture by 

 its foliage, into the air of the room. This would be equivalent to evaporat- 

 ing half a pint of water upon the stove. A dozen plants of the same kind 

 must, therefore, give out six pints of water, in the sliape of invisible vapor, 

 into the dry atmosphere of the chamber, and thus effectually counteract 

 that unwholesome dryness which proceeds from the use of coal fires and 

 close stoves. It is this invisible moisture, produced in a form more whole- 

 some and agreeable than when evaporated directly from heated water, that 

 renders the atmosphere of a greenhouse so soothing and delightful, com- 

 pared with that of a sitting room of the same temperature. 



Plants Injured by Brick Flues. — There has a circumstance come 

 under my observation this winter, about which I wish to gain some informa- 

 tion, and as you have had so much experience in horticultural matters and 

 seemingly have improved every opportunity it has given you of taking 

 observations on almost every thing connected therewith tliat has transpired 

 during your successful career, I am induced to apply to you for the informa- 

 tion desired. 



Last autumn (1854,) I had charge of putting up a small structure to be 

 used as a hothouse, or a place to keep such plants in as needs a little more 

 heat than a greenhouse commonly affords, or ought to afford, which was to 

 be heated by a common smoke flue. Well, I got all finished up in good 

 order, as I thought, ready for the reception of the plants, (having tried the 

 draft of the flue, &ic.,) and every thing seemed to be to my entire satisfac- 

 tion; Accordingly, when the proper time came, the plants were put into 

 the house and all went on well, until the advance of the season required 

 the flue to be heated up pretty hot. The first morning afler there had been 

 a pretty strong fire on during the night, I perceived the tips of the leaves 

 of some of the most tender things blackened and curled up, which I could 

 not particularly account for, but supposing it to be caused by some of the 

 noxious gases sometimes emitted from bad coal that had escaped someway, 

 or the heating of the half-dryed green paint with which the house was 

 painted, (that sometimes has a bad effect on plants,) it passed from my 

 mind until it happened again and again, and as the season advanced in 

 cold it was of more frequent occurrence, and produced more detrimental 

 effects, until one night I had occasion to go from home and leave the 

 charge of heating the house to a rather inexperienced hand, who heaped 

 on the fire during the night and raised the temperature to about 65 Fahren- 

 heit ; consequently the next day the plants presented a sorry spectacle. 

 Almost every leaf of every plant in the house, except a few Ixoras, Jasmin- 



