230 Natural- Philosophical Collections. 



The rationale of this curious excrescence now seems to me perfectly evident, as 

 demonstrated by the preparation in my possession* In the first place, the in- 

 ferior surface of the undissolved metal was acted on by the nitric acid remaining 

 in the interstices of the general crystallization. By continued action of this kind 

 the globule was elevated, and by capillary ascent fresh supplies of the acid were 

 afforded, until the weight of the metal overpowered the moist pedicle on which it 

 rested, and which accordingly arched over, and rested again on the general sur- 

 face ; again the same operation occurred here, till at length the growth was finally 

 arrested by the total exsiccation of the mass. 



I have since tried to procure this vegetation of the proto-nitrate by designed 

 arrangement, and find I can always succeed in the formation of beautiful, though 

 fentasticj excrescences, by adhering to the same proportions, and using the same 

 little vessel employed in the experiment I have just narrated. 

 Edinburgh, \8th May 1830. 



Discovert/ of Salicine, a powerful Febrifuge..^Ai the Academy of Sciences, 

 on the 10th of last month, M. Magendie, in his own and M. Gay-Lussac's name, 

 gave a very favourable report on a memoir by M. Leroux, an apothecary at Vitry- 

 le-Francais, relative to a new substance which he has extracted from willow-bark, 

 and to which he gives the name of salicine. This substance presents itself under 

 the form of white crystals, having a very bitter taste resembling that of willow- 

 bark. He considers it as a vegetable alkali, and thinks that by combining it 

 with sulphuric acid he has obtained a sulphate of salicine. He has also ascertain- 

 ed that salicine possesses febrifuge properties. The commissioners, however, on re- 

 peating the observations of M. Leroux, found that the substance which he calls 

 salicine is not an alkali. It does not saturate acids, but is decomposed by them ; 

 so that no sulphate of salicine exists. As to the medical properties of salicine, 

 the commissioners have ascertained that they are in reality very powerful, and 

 that the substance in question may be advantageously employed instead of qui- 

 nine. M. Magendie administered it in doses of 18 grains per day, at three 

 several times, six grains at each, and this quantity he found sufficient to repel in- 

 termittent fevers. At the request of the commissioners, experiments have been 

 made with salicine in several of the Paris hospitals, and particularly in the Hotel- 

 Dieu and La Charity, and it has always been found that the quantity of from 18 

 to 24 grains, at the most, administered in doses of six grains, was sufficient to 

 prevent the return of the accession. The dose of salicine necessary for obtaining 

 this effect is therefore really inferior to that of quinine which would be required 

 in the same circumstances. The commissioners were of opinion that M. Lerotix* 

 discovery is one of the most important with which medical science has been en- 

 riched of late, and recommended that the Academy should express the most entire 

 approbation of his labours, encourage him to continue his researches, and advise 

 him, in particularj to undertake the preparation of salicine on the large scale, 

 that it may become generally used. Three pounds of the willow-bark yield an 

 ounce of salicine 5 and if the extraction were carried on to a great extent, it is 

 probable that the same quantity of bark would yield two ounces. 



of Diana, &c. depend upon this principle, as has been demonstrated by Grott» 

 huss, (Ann. de Cnim. t. Ixiii.) The tree of Saturn is formed by immersing a 

 blade of zinc in a solution of acetate of lead. The zinc is oxidated, and at every 

 moment that a lamina of metal deposits itself at the extremity of a branch, and 

 gives it an additional growth, the oxygen which it has quitted combines with 

 the zinc. The zinc and the lead constitute a pile which decomposes the ace- 

 tate and oxide of lead, attracting the metal to the negative pole, the oxygeft 

 to the positive. 



The same principle may be applied to the formation of the tree of Diana, 

 obtained by pouring a concentrated solution of nitrate of silver on mercury, 

 — to similar appearances obtained by immersing a blade of zinc in a solution 

 of the hydro-chlorate of tin,— and to the phenomena which have been the ob- 

 ject of Dr. O'Shaughnessy's interesting communication. Ed. 



