296 Mr F. Marcet on the Action of' Poisons 



Exp. 8L — On the 10th May 1824, Mr Marcet introduced 

 into a hole in the stem of a cherry tree, which penetrated in- 

 to the pith, some drops of metallic mercury, and covered up 

 the hole. On the 10th March 1825, the tree had suffered no 

 injury, although it has been said that trees are killed by that 

 process. 



TIN. 



On the 13th April, a rose tree branch with two or three 

 buds, was introduced into a solution of muriate of tin, of the 

 same strength as the preceding solution. On the 15th, brown 

 streaks appeared along the ribs of the leaves, larger and of a 

 deeper colour than those produced by muriate of mercury. 

 On the 16th the branch was dead, and the leaves almost all 

 yellow. 



Tin acted upon French beans exactly like the muriate of 

 mercury. 



COPPER. 



In a solution of sulphate of copper, of the same strength as 

 the preceding one, a French bean plant, taken from the 

 ground, was immersed by its roots. The bean withered at 

 the end of a day ; but it required several waterings, and more 

 copper, to kill it completely. 



LEAD. 



A French bean was introduced by the root into a solution 

 of acetate of lead, of the same strength as the preceding. The 

 lower leaves withered at the end of two days, but it did not 

 die till the end of the third. 



The same thing happened with the Muriate of Barytes. 



Mr Marcet next tried the effects of sulphuric acid, potash, 

 and sulphate of magnesia. 



French bean plants being introduced by the root into sul- 

 phuric acid diluted with three times its weight of water, they 

 began to droop at the end of a few hours, and, at the end of 

 a day, they withered. 



The same effect was produced by the action of liquid pot- 

 ash diluted with the same quantity of water. 



Plants of French beans were not, in the slightest degree, in- 



