Glass Case for gro'wing Plants in Rooms. 



117 



Art. VIII. Description of a Glass Case for groming Plants in Rooms- 

 By Sir John Robison, Sec. R.S.E. 



I HAVE been fretting up a plant case of the kind described in 

 the Gardener's Magazine for 1839 (p. 481.), in which I think I 

 have introduced some essential improvements : 1st, instead of an 

 expensive brass frame for small panes of crown glass, I have 

 substituted four sides and a flat top of plate glass, which, requiring 

 only corner astragals and 

 a top frame of wood, is 

 cheaper than the other, 

 and greatly better looking. 

 The sketch Jig. 15. will 

 serve to give you some 

 idea of it. The principal 

 innovation is, in providing 

 for the perfect isolation of 

 the air within the case from 

 commixture with the air of 

 the apartment it may be 

 placed in. It appearing to 

 me that the contraction of 

 bulk consequent on re- 

 duction of temperature during the night, must necessarily cause 

 an introduction of air from the apartment at a time when it 

 was most likely to be contaminated with sulphuretted hydrogen 

 from the gas lights and other causes, I have introduced a small 

 tube through the bottom of the case, passing upwards to the 

 surface of the soil. On the exterior end of this tube there is a 

 coupling screw, by means of which I connect it with a flat bag of 

 M'Intosh cloth hung under the case, half-full of good air at 

 the time of its attachment : the alterations of bulk consequent on 

 changes of temperature, therefore, are provided for by the dila- 

 tation or shrinking of the bag, and no pressure is ever exerted 

 to pass air through the joints of the case. Unless, therefore, 

 the plants themselves cause a permanent change in the con- 

 stitution of the air (which some of the best-conducted experiments 

 seem to render improbable), it will remain unvitiated, and be 

 subjected to those compensating changes only which the plants 

 appear to make in light and darkness. 



I do not mean to fill the case with permanent plants until 

 May next, and in the mean time shall make use of it to flower 

 hyacinths, &c. If you have attended to the subject of Mr. 

 Ward's system, and should choose to suggest any experiments 

 which the condition of this case may render practicable, I shall 

 be happy to undertake them for you on your explaining your 

 wishes. 



