486 



made exactly suitable. Above all, the health of the animal will not be 

 endangered, as is done by the old proceeding. The professor calculates 

 that in the average 0,040 units of heat are consumed in the evapora- 

 tion of the adhering water, which he thinks too heavy a tax on the 

 animal econoiny. 



Nitrous and nitric acids in soils. — Investigations have lately 

 been prosecuted by Chabrier upon the presence and functions of nitrous 

 acids in soils. The soils examined were finely powdered and passed 

 through a sieve, and then bleached, according to the method adopted in 

 the saltpeter works of Algiers, for the purpose of determining the per- 

 centage of nitrous and nitric acids. As the result, it was ascertained 

 that all tilled soils contained nitrous acid. Mtric acid, as is well known, 

 is accumulated, especially in dry weather, in the superficial strata of the 

 earth, the reverse being the case with the nitrous acid. Hence, it would 

 seem that the soluble nitrates ascend in the soil bj^ capillarity in dry 

 w^eather, when they are transformed, at least in part, into nitrates, 

 which, on the other hand, are washed out by the rain. The water of the 

 soil generally contains 1 part of nitrous acid to 25,000 parts of water; 

 never more than 1 part in 5,000. Fields which have lain fallow con- 

 tain little nitrous acid but much nitric acid ; while, on the other hand, 

 forest land contains moderate quantities of nitrous and but little nitric 

 acid; and inundated clay no nitrous and but little nitric acid. Tlie au- 

 thor is of the opinion that the nitric acid, in spite of its slight percent- 

 age, is of importance in the earlier i)eriods of vegetation. 



Disposal of the nitrogen of manure. — Prom more than twenty 

 years of experiment, Laws & Gilbert have ascertained that harvest 

 plants do not by any means take up all the nitrogen which has been 

 put into the soil in the form of manure, or of ammonia, or other concen- 

 trated substances. Even if land be manured witli the same amount of 

 nitrogenous matters, and the same i)lants be cultivated, not half of the 

 nitrogen is abstracted from the manure. Of the remainder, a certain 

 part is to be met with in the form of ammonia in the drainage water, 

 and a considerably larger amount occurs therein as nitric acid, a large 

 part of the nitrogen being abstracted from the manure in this way. Of 

 what is left, however, a very considerable portion is accumulated in the 

 soil, and is carried into its deeper strata. 



SoRBT ON tints OF FOLIAGE. — We have already referred to the in- 

 vestigations of Sorby in regard to the various tints of foliage, and 

 especially to the change of color .in the leaves in autumn ; and in a late 

 number of "Nature" we find a resume by him, giving the present state 

 of his inquiries on the subject. He separates the different coloring mat- 

 ters into five groups: first, the chlorophyl group, characterized by being 

 insoluble in water, but soluble in alcohol and in bisulphide of (;arbon, 

 and embracing three or four species; second, the xanthophyl group, 

 containing several species, only two of which are common in leaves, one 

 being more and the other less orange. They are characterized by being 

 insoluble in water, and soluble in alcohol and in bisuljdiide of carbon, 

 differing, however, from the members of the first-mentioned group in 

 having peculiar spectra; third, the erythrophyl group, comjuising a 

 number of colors soluble in water, in alcohol, and in ether, but insoluble 

 in bisulphide of carbon. Tliose met ^vith in leaves are more or less pur- 

 ple, are made bluer by alkalies and redder by acids ; and thus sometimes 

 plants containing the same kind may vary more in tint, owing to a va- 

 riation in the amount of free acid, than others colored by entirely differ- 

 ent kinds. Among the species some have very interesting botanical 



