1813.] Imperial Institute of Fra?ice. 395 



But it was destined for the writers of our days to explain and 

 support, by numerous examples, the advantage of proper rota- 

 tions. M. Yvart, one of those who has paid most attention to 

 the subject, has the merit of drawing all his from the soil of 

 France itself. His instances are very numerous. He has given 

 them for all climates, for all exposures, for all varieties of soil. 

 He has shown that we may every where suppress the fallows, and 

 introduce in their place a rotation of crops much move produc- 

 tive, and capable of retaining all the fertility of the soil. 



M. Hassenfratz, divisionary inspector of mines, charged by 

 government to publish a tre itise on metallurgy, has submitted 

 to the Class the first part of it, entirely devoted to the extraction 

 of iron from its ores, on account of the importance of this metal 

 for the arts, and the numerous works required by the different 

 modifications of which it is susceptible. It has been found that 

 the facts contained in thi* work are arranged in a natural order; 

 that all the processes are explained with clearness ; and that it 

 may be considered as a general collection of every thing known 

 respecting iron, either from books, from workmen, or iron- 

 masters. This first part has been recently published. 



tmhm«^ i nn i f 



Article XIV. 



scientific intelligence; and notices of subjects 

 connected with science. 



I. Ulmin. 



Notwithstanding the various observations and experiments 

 which 1 'nave had an opportunity of making on ulmin, it is only 

 lately that 1 have been so fortunate as to meet with it in a state 

 of purity, so as to be able to ascertain its real properties, and to 

 assign it a true place among vegetable substances. 



1 received some time ago from Dr. Leach a specimen of a 

 black matter which he had collected on an oak in the neigh- 

 bourhood of Plymouth. It turned out, on examination, to be 

 ulmin quite free from potash, a substance which had constituted 

 a part of all the specimens formerly examined either by Mr. 

 Smithson or myself. 



It was in small lumps, mostly attached to each other by 

 vegetable fibres, lis colour was a very dark brown, almost 

 black. It had little or no taste. It was considerably firmer than 

 the ulmin mixed with potash, and of a greater specific gravity. 

 I found its properties as follows : — 



l . Nearly tasteless. 



_'. Dissolves very slowly, and in small quantity, both in water 

 and alcohol. The solution is pale brown, and tasteless. 



