142 Drs Turner and Cliristison on the effects of 



" especially to the sulphurous acid, that our attention was drawn 

 in the first instance. 



The Sulphurous acid gas appears to be exceedingly delete- 

 rious to vegetables, even in very minute quantity and propor- 

 tion. We first observed that when four, or even only two cu- 

 bic inches were introduced along with a young mignonette 

 plant, into the air of a glass jar of the capacity of 470 cubic 

 inches, the leaves of the plant became greenish-gray, and 

 drooped much in less than two hours and a half ; and though 

 then taken out and watered, it soon died altogether. We 

 next found that when somewhat less than half a cubic inch 

 was introduced into a jar of the capacity of 509 cubic inches, 

 a mignonette plant introduced along with it began to lose its 

 colour and to droop in three hours ; and although taken out 

 three hours after that it languished, and gradually died in the 

 course of a few days. 



But the peculiar effects of the gas, and its extraordinary de- 

 structiveness, are better shown when its quantity and propor- 

 tion to the air are still less, — as, for example, in the following 

 experiment. A wide-mouthed bottle, containing a mixture of 

 six cubic inches of air and /o^^thsof acubicinch of sulphurous 

 acid, was fixed, mouth uppermost, on a stand twenty inches 

 high ; — at the bottom stood a young mignonette plant, a young 

 laburnum tree six inches tall, and a young larch, which had 

 been all transplanted at least five days before, and had recent- 

 ly been well watered ; — and over the whole was placed and 

 carefully luted to the table a glass jar two feet high, and of 

 the capacity of 2000 cubic inches, so that the proportion of 

 sulphurous acid was nearly a 9000th part. The jar stood in 

 a situation where it was exposed to a bright diffused light, 

 but not to the sunshine. We had previously found in a simi- 

 lar experiment with a mignonette plant alone, that it became 

 affected in less than twenty-four hours ; and in a subsequent 

 experiment with a laburnum visible effects were caused by 

 the same quantity and proportion in nine hours. In the pre- 

 sent instance, on account of the large surface of moist earth 

 exposed, which would absorb some of the gas, the effect was 

 slower and less complete. In forty-eight hours, however, all 



