SCIENTIFIC COMMITTEE, NOVEMBER 1. 



Iv 



is that the plant-house must be air-tight. As glass houses, 

 however, are usually and purposely constructed with air spaces 

 beneath the overlapping glasses, these would have to be stopped 

 up. In a house properly constructed, like that erected by Mr. 

 Toope, the external air entered below, and was passed through 

 boxes containing charcoal. A draught is created by the heated 

 air of the house, which escapes at the top by means of exhaust 

 caps, which allow of the passage of air from but not into 

 the house. No sulphurous acid whatever then succeeded in 

 passing through the carbon into the house, the nitration 

 appearing to be perfect. A second method suggested was by 

 means of sprays of various kinds, and by sprinkling the floors, &c. 

 This method has its disadvantages, and Prof. Oliver did not 

 express a favourable opinion of it. The third plan is simply to 

 spread canvas over the house during the period of the fog to 

 prevent its passing through the cracks and into the house. Of 

 course the stoppage of light might be, in some circumstances, a 

 serious objection, but not greater than that occasioned by the fog 

 itself. The really injurious element of fogs is undoubtedly the 

 sulphurous acid gas, and this has to be specially combated. A dis- 

 cussion followed as to what steps should be taken by the Society 

 in the matter. It was generally felt that, as far as the Scientific 

 Committee were concerned, they could not do more than under- 

 take the first object mentioned by Dr. Eussell ; and this has, in 

 fact, been done. The second and wider object, however, is more 

 or less directly concerned with the former, though it may have 

 a much wider scope. It was proposed, therefore, to make a 

 statement as to what the Royal Horticultural Society has already 

 done in the matter, and to invite the co-operation and assistance 

 of other societies, such as the Meteorological ; finally, to appeal 

 to the County Council to take steps towards carrying out a more 

 extensive investigation than the small funds at the Society's 

 command alone could possibly accomplish. 



Termes lucifugus. — Mr. McLachlan corrected an error in the 

 description of the white ant of La Rochelle, as to the size of the 

 larvae, in that they are really smaller than stated, being less than 

 a quarter of an inch in length. 



Artichoke- Gall. — Mr. McLachlan also exhibited a specimen of 

 this disease on the Oak, alluded to at a previous meeting. It is 

 produced by Aphilotrix fecundatrix, of which the agamic genera- 

 tion is known as Andricus noduli. 



