512 Drs. Will and Fresenius on the 



taken from a given sui'face by the crop. Rational agricultu- 

 rists and woodreeves are always in possession of details of this 

 kind, which are generally of sufficient accuracy for the ends 

 to be answered by them. 



The vegetable substance under examination should be dried 

 over a water-bath at 100° C. until it no longer loses weight ; if 

 however any of its constituents be volatile, tiie drying is best 

 conducted over sulphuric acid, without the application of heat. 

 The quantity of substance to be burned to ash will depend 

 upon the quantity of fixed matter it contains. Of herbs and 

 seeds, which are rich in inorganic constituents, 2 to 3 grammes 

 will be sufficient ; of woods, however, which frequently contain 

 only 0*2 per cent, of fixed matter, ten or more times that 

 quantity must be taken. The combustion succeeds best in a 

 thin platinum crucible ; it is at first covered and heated only 

 gently, but afterwards the lid is removed and a stronger heat 

 employed until the whole of the charcoal is consumed. The 

 ashes of seeds which do not effervesce with acids may be 

 moistened with nitric acid and re-ignited, when they will very 

 speedily be turned white. 



We now submit a number of ash-analyses which were con- 

 ducted according to the methods we have described. The 

 first are those of ten kinds of tobacco, which were sent to 

 Professor Liebig for the purpose by the director of the Im- 

 perial Austrian tobacco manufactory in Vienna. All these 

 plants were cultivated in Hungary, upon land which had never 

 been manured, and upon which the same plant had been grown 

 for a considerable length of time. 



The specimens 1, 2 and 3 were from the Debreczyner, No. 

 4 from the Banat, and Nos. 5 to 10 inclusive from the FUnf- 

 kirchner district. With the exception of Nos. 7, 8, 9 and 10, 

 the leaves reached us in a sound and perfectly healthy state, 

 still partially retaining their green colour. Differences were 

 however clearly indicated by the varying size and greater or 

 less luxuriance of the specimens. 



In addition to the above we analysed the ashes of the grain 

 of red and of white wheat ( Triticum vulgare), of the seed and 

 of the straw of rye {Secale Cercale), of peas [Pisum sativum), 

 of the wood of the apple-tree {Pyrtis mains), of the mistletoe 

 {Viscum album) from the same tree, and of lichens {Parmclia 

 prunastrif fraxinea, parietina, furfuracea) : all were grown 

 in the neighbourhood of Giessen. 



