THOMAS ANDREW KNIGHT, ESQ. 35 



other, in your experiments, with a more abundant portion of 

 food than it would otherwise obtain ; and I have shown that 

 the wood of a fir-tree above such a decorticated space, was one- 

 fifth larger than the wood of the same tree below : the specific 

 gravity of the one being 0.590, and that of the other only 0.491. 

 Your experiment, like the preceding, which is in the Philoso- 

 phical Transactions, of 1806, affords, I think, strong evidence 

 in support of my theory, in which the sap is supposed to descend 

 down the bark ; and on that, as well as other accounts, is very 

 acceptable to me. 



" I had occasion to write to Sir Joseph Banks the day after 

 I came home, and I sent him an account of your experiments 

 on the vine, with which I am sure he will be much pleased. I 

 think an account of them would be very well received by the 

 Horticultural Society*. I feel greatly interested in them, I 

 assure you, both as a gardener and as they afford strong evidence 

 in support of my opinions respecting the circulation of the sap. 



" I remain," &c. 



The two letters that follow relate to some experiments on the 

 effects of voltaic electricity on vegetable life, which Mr. Williams 

 had undertaken at the suggestion of Sir Joseph Banks and Mr. 

 Knight, whose attention had been directed to this subject, by 

 experiments made by Dr. Wilson Philip, proving the powerful 

 influence of a current of electrical fluid when applied to the 

 digestive organs of animals ; while by some other writers it had 

 been denied that any effect was produced by similar application 

 of electricity. 



Some seeds of the J^iciafaba were subjected by Mr. Williams 

 during the process of germination to a current of voltaic elec- 

 tricity, and the result was, that vitality was quickly destroyed 

 by a strong charge ; and that even the slightest that could be 

 given produced a manifestly injurious effect on the plant, and 

 destroyed it when long persisted in. One remarkable effect 



* A paper on " A method of hastening the maturation of grapes," was com- 

 municated to the Horticultural Society by Mr. Williams, May 3, 1808. 



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