36 LIFE OF 



apparent was, that when the radicle ceased to vegetate, it did 

 not change colour like a decaying root from end to end, but in 

 alternate rings of black and white. Mr. Williams thought this 

 effect probably indicated that some parts of the organization of 

 the root were more susceptible of the electrical influence than 

 others, but considered that it deserved further investigation. 



/ 

 "January 3, 1818. 



" MY DEAR SIR, 



" I have had so much writing on my hands, that I had not 

 at once eyes and time to write to you sooner, which must plead 

 my excuse for my apparent inattention. 



" The metallic oxydes still stand, I think, too prominent ; 

 and I, if I had not seen the experiment, should, as a member 

 of the Royal Society, on hearing the paper read, be more dis- 

 posed to attribute the death or sickness of the plants to the 

 operation of metallic poison, than to the voltaic battery. No 

 one can possibly rob you of the discovery you have made, as my 

 correspondence with Sir Joseph Banks upon the subject will 

 prove. You will, I hope, still appear in the same part of the 

 Transactions*. 



" I think it expedient that a few more experiments be made, 

 as soon as you begin to warm your vinery. There can be little 

 difficulty in proving whether oxyde of iron, that is, the red 

 oxyde, which I suppose to be the kind produced by the voltaic 

 battery, is poisonous to plants, by putting a dozen rusty nails 

 into a tumbler of water with plants. I am of opinion that it 

 would not produce the least injury ; for red soils (which are 

 much more fertile than pale yellow and white) contain about 

 thirteen per cent, of red oxyde, and plants are well known not 

 to be destroyed by strong chalybeate springs. 



" Many beans may be placed over a tumbler of water, with 

 their radicles descending into the water, through which a strong 

 stream of galvanic electricity may be made to pass, as in your 



* Mr. Williams' paper was read before the Royal Society, but was not 

 printed in the Transactions. 



