LEVELS OF FRANCE. 34! 



fiioisture : and a strong heat causes it to rise in the form of 

 a thick oil, the smell of which is that of an animal sub- 

 stance, and unpleasant. A little carbonate of ammonia 

 accompanies it. It leaves very little coal. But what dis- Soluble in 

 tinguishes it from the aromatic vegetable resins is its great aIkalls - 

 solubility in the weakest alkalis. Acids separate it from 

 these without alteration, and it may be drawn out into jj ot a i wa ys the 

 threads as before ; so that we cannot deny it the principal same. 

 characters of resins, but it is not always the same. I have 

 obtained some from gall, which was soft, semifluid, or in- 

 capable of assuming the consistency of the preceding. 



To obtain this resin pure, Ave must begin with passing Mode of ob- 

 dried gall through alcohol, to separate its albuminous por- tainm S xt P ure » 

 tions. These occasion the putrefaction of gall when kept: and preserving 



but the extract, passed through alcohol, and evaporated to 8 a! i from P u ~ 



\ . . , ., , „ , trefactioa. 



the consistence of a sirup, is no longer susceptible of alte- 

 ration; and it is in this state I keep it for my lectures*. 



VII. 



Remarks on the Structure of Mount Jura, from a con- 

 siderable Ntimber of Heights taken by the Barometer, 

 and extended through Fra?ice to the Sea ; by Mr. And. 

 de Gy ? Member of the Academy of Cassel, Sfc. + " 



1. JL HE four loftiest summits of the first chain of the Jura First chain ©f 

 are nearly on a level, as is their base, the lake of Geneva, mount Jur *> 

 on a length of twelve leagues. 



The summits of the Suchetand Sucheron, which rise from 

 the western extremity of the lake of Neufch&tel, six leagues 

 from the preceding, are 30 toises lower. The other sum- 



* An ingenious artist, Mr. J. Clark, in his Instructions for Draw- 

 ing and Painting in Water Colours, observes that gall, which it is 

 frequently necessary to add to a tint, when it will not adhere uni- 

 formly to the paper, from any slight greasiness of its surface, will 

 keep much better, if it be boiled a little. This no doubt is owing 

 to the coagulation and separation of the albuminous matter by heat, 

 conformably to the remark of Professor Proust. W. N. 

 t Journal des Mines Vol. XVIII. p. 430, 



