276 Dr. Ure 07i Soda- Alum. 



many established laws of the nervous system, I have consi- 

 dered at some length in the ninety-sixth and following pages of 

 the second edition of my Treatise on Indigestion. It appears, 

 as far as I can judge, from the facts there adduced, that it is 

 altogether unfounded, the nerves seeming in the latter as in the 

 former case, only to convey impressions made on their extre- 

 mities to the more central parts of the system. 

 (To be continued) 



Art. IV. On Soda-Alum, in a Letter from Dr. Ure to 

 Dr. Wollaston, V. P. R. S. 



Glasgotv, March 1, 1822. 

 Dear Sir, 



I now fulfil the promise which I made at my visit to 

 London, in October last, of sending you specimens of soda- 

 alum, a salt, concerning whose existence, or possible formation, 

 our ingenious friend, M. Clement'-Desormes, expressed, as you 

 may remember, the strongest doubts. The larger crystals were 

 made by Mr. William Wilson, an extensive'alum-manufacturer 

 in this neighbourhood ; the smaller and more regular ones were 

 formed by myself in the following way. 



In a cold lixivium of effloresced alum schist, of specific 

 gravity, 1.35, previously freed by crystallization from the 

 greater part of its sulphate of iron, I dissolved with trituration 

 in a glass mortar nearly as much muriate of soda as the liquid 

 would take up. The solution was then left to spontaneous 

 evaporation, in a temperature of about 60° F. At the end of 

 two or three weeks, abundant groups of regular octohedrons 

 were found difiused throughout the yellowish pasty magma. 

 These crystals were washed with alcohol, and dried with 

 blotting paper. To free ihem entirely from an adhering portion 

 of copperas, they must be re-dissolved and re-crystallized. 



The form and taste of this salt are exactly the same as 

 those of common alum ; but it is less hard, being easily crushed 

 between the fingers, to which it imparts an appearance of 

 moisture. Its specific gravity was determined by weighing in 



