224 



'Gardeners' Magazine' for September, 1839, that part which relates 

 to the observations and experiments of Drs. Turner and Christison 

 on the effects of sulphurous and muriatic gases upon vegetation, the 

 author observes : — 



" The conrectness of the above ohservations of Messrs. Turner and Christison, as 

 to the effects of sulphurous and muriatic acid gases upon plants, cannot for one mo- 

 ment be doubted ; and that plants suffer when exposed to a direct current of these 

 gases, before there is time for diffusion through surrounding space, is equally matter 

 of fact ; but I contend, that it yet remains to be proved that there exists generally in 

 the atmosphere of London, or other large cities, such a proportion of these noxious 

 gases as sensibly to afiect vegetation. We shall find in the windows of shops and 

 small houses, in numerous parts of London, hundreds of geraniums and other plants, 

 growing veiy well and without any crisping or curling of the leaves, care being taken 

 in these instances to keep the plants perfectly clean and free from soot ; and it is certain, 

 that although my cases can and do exclude the fuliginous portion of the atmosphere, 

 and certainly protect the plants from the effects of any direct current of hurtful airs, 

 they cannot exclude that portion which becomes mixed with the atmosphere." — p. 17. 



The author gives various examples of the rapidity with which gases 

 mingle with each other and with the atmosphere, under the influence 

 of " a law constantly in action under all circumstances " and in all 

 places, by means of which the several constituents of the atmosphere 

 are ever preserved in their respective proportions. 



Chap. III. — On the Imitation of the Natural Conditiojis of Plants 

 in closely glazed Cases. At the commencement of this chapter the 

 author gives such a pleasant description of the fi-ustration of his early 

 attempts to obtain something like country within the smoke of Lon- 

 don, and of the occurrence which led to his subsequent success, that 

 we must quote the passage entire. 



" The science of Botany, in consequence of the perusal of the works of the immor- 

 tal Linnaeus, had been my recreation from my youth up ; and the earliest object of 

 my ambition was to possess an old wall covered with ferns and mosses. To obtain 

 this end, I built up some rock-work in the yard at the back of my house, and placed 

 a perforated pipe at the top, from which water trickled on the plants beneath ; these 

 consisted of Polypodium vulgare, Lomaria spicant, Lastrasa dilatata, L. Filix-mas, 

 Athyrium Filix-fcemina, Asplenium Trichomanes, and a few other ferns, and several 

 mosses procured from the woods in the neighbourhood of London, together with prim- 

 roses, wood-sorrel, &c. Being, however, surrounded by numerous manufactories and 

 enveloped in their smoke, my plants soon began to decline, and ultimately perished, all 

 my endeavours to keep them alive proving fruitless. When the attempt had been given 

 up in despair, I was led to reflect a little more deeply upon the subject in consequence 

 of a simple incident which occurred in the summer of 1829. I had buried the chry- 

 salis of a Sphinx in some moist mould contained in a wide-mouthed glass bottle, co- 

 vered with a lid. In watching the bottle from day to day, I observed that the mois- 

 ture which during the heat of the day arose from the mould, became condensed on the 



