175 



the slightest degree of sweetness in decoctions of the wood in winter. 

 He therefore is inclined to believe, that the saccharine matter is ge- 

 nerated by a process similar to that of the germination of seeds ; and 

 that the said process is always going on during the spring and sum- 

 mer ; but that towards the conclusion of the summer, the true sap 

 simply accumulates in the alburnum, and thus adds to the specific 

 gravity of winter-felled wood, and increases the quantity of its ex- 

 tractive matter. He says also, that he has some reasons for thinking 

 that the true sap descends through the alburnum, as well as through 

 the bark ; and that he has been informed, that if the bark be taken 

 from the trunks of trees in the spring, and such trees be suffered to 

 grow till the following winter, the alburnum acquires a great degree 

 of hardness and durability. 



Mr. Knight concludes by observing, that he conceives himself to 

 be in possession of facts, which prove that both buds and roots ori- 

 ginate from the alburnous substance of plants, and not, as he believes 

 is generally supposed, from the bark. 



On the Action of Platina and Mercury upon each other. By Richard 

 Chenevix, Esq. F.R.S. M.R.I.A. &c. Read January 10, 1805. 

 [Phil. Trans. 1805,^. 104.] 



Mr. Chenevix, in the month of May 1803, presented to the Royal 

 Society a paper, which was printed in the Philosophical Transactions 

 for that year, respecting the nature of a metallic substance which 

 had been offered to the public as a new simple metal, under the name 

 of Palladium. In that paper he not only attempted to prove that the 

 said substance, instead of being a simple metal, was merely a com- 



rnd of platina and mercury, but he also described certain processes 

 which he had been enabled to produce it. He now expresses his 

 mortification to learn that the processes he there recommended, as 

 the least likely to fail, have been generally unsuccessful ; and con- 

 fesses he has reason to believe " that the nature of palladium is con- 

 sidered by most chemists as unascertained, and that the fixation of 

 mercury by platina is by many regarded as visionary." 



In France, he says, the compound nature of palladium has been 

 more generally credited ; M. Guy ton, who was appointed by the 

 National Institute to make a report upon Mr. Chenevix's experiments, 

 having repeated some of them, and having been led by the results to 

 the same general conclusions as Mr. Chenevix. 



Messrs. Fourcroy and Vauquelin also made some experiments 

 upon the subject ; but as about this time a new metal had been dis- 

 covered in crude platina by Mons. Descotils, the above-mentioned 

 chemists were led to suppose it probable that the new metal was 

 concerned in the production of palladium ; and finally declared, as 

 their opinion, that the substance called palladium does not contain 

 mercury, but is formed of platina and the new metal of M. Descotils. 

 Mr. Chenevix adduces several arguments to show that this opinion 

 is not well founded ; and in the latter part of his paper, he says, that 



