42 Mr. T. Taylor on some 



merits as to its nature*. The result of a careful comparison 

 of the chemical characters of these concretions with those of 

 ellagic acid prepared from the gall-nutf so fully established 

 their identity, that I did not think it necessary to corroborate 

 my statement by an ultimate analysis, especially as from the 

 limited quantities of the calculus on which I could operate, and 

 the facility with which ellagic acid becomes oxidized when 

 dissolved in an alkali, I did not feel certain that I could en- 

 sure that perfect purity without which an organic analysis is 

 wholly valueless. Its ultimate analysis has however been made 

 by MM. Merklein and Wohler, who have found it to agree 

 with the analysis of ellagic acid by M. Pelouze, minus one 

 atom of hydrogen. 



The following description of the ellagic acid calculus, its 

 properties and history, 1 shall quote verbatim from the Col- 

 lege Catalogue published in July 1845, as it conveys in a con- 

 densed form the results of a long and troublesome series of 

 experiments. 



" Ellagic acid calculi are generally of an ovoid figure ; their 

 outer surface is smooth, polished, and of a deep olive or 

 greenish brown colour; internally they are brown; they are 

 made up of thin concentric layers, which in some cases adhere 

 so slightly together, as to cause the calculus to fall to pieces 

 on attempting to divide it with a saw. When any of the 

 outer layers of these calculi are removed, the exposed surface 

 readily acquires a high polish by slight friction, and when cut 

 or scraped they assume a waxy lustre. These calculi in- 

 variably contain some foreign body as their nucleus, which is 

 generally a small twig or seed. 



* Ann. der Chemie und Pharm-, August 1845. If by the following pas- 

 sage, " Aus dieser Zusammensetzung und den oben angegebenen Eigen- 

 schaften der Bezoarsaure folgt ferner der merkwurdige Umstand.dass diese 

 Substanz, wie bereits von Th. Taylor verniuthet wurde, in der That nichts 

 Anderes ist als Ellagsaure oder die Siiure, die zuerst von Chevreul aus den 

 Gallapfeln dargestellt und von Braconnot naher untersucht worden ist. 

 Um nicht den geringsten Zweifel hieriiber zu lassen, haben wir selust El- 

 lagsaure aus Gallapfeln dargestellt und ihre Eigenschaften init denen der 

 Bezoarsaure verglichen; sie zeigten sich vollkommen identisch,'' MM. 

 Merklein and Wohler intend to imply that some doubt existed in my mind 

 as to the composition of this concretion, I beg to state that such was not 

 the case; and it is difficult to conceive on what grounds they could form 

 such an opinion, as in the notice alluded to I simply stated the fact in the 

 most concise and positive terms that could be made use of. 



f For the opportunity of doing this on rather a large scale, I am in- 

 debted to my friend Mr. T. Morson, who kindly placed at my disposal a 

 large quantity of the residue left in the preparation of gallic acid, and it 

 gives me much pleasure to have an opportunity of acknowledging this and 

 similar favours. 



