I. AGRICULTURE AND RURAL ECONOMY. 403 



Passing from the effects of heat to those of freezing, Verg- 

 nette-Lamotte considers that light wines containing little al- 

 cohol and little acid, and very thin wines, may have their 

 value doubled by freezing. His process is of no use either 

 for common wines or for those which already possess all the 

 qualities demanded from a first-rate vintage. 3 A, June 15, 

 1872,515. 



ARTIFICIAL HUMOUS SUBSTANCES. 



One great difficulty experienced by Dr. Detmer in the in- 

 vestigation of humous bodies was in their preparation in a 

 pure condition from natural sources ; but, while studying the 

 well-known action of sulphuric acid on cane-sugar, he found 

 that by boiling 3000 grains of sugar in 9000 grains of water 

 and 900 grains of concentrated sulphuric acid, a considerable 

 amount of humous matter was formed, which gave reactions 

 identical with those of natural humus ; and also that, con- 

 trary to the views of Mulder, the brown substance obtained 

 by boiling sugar only for a quarter of an hour in dilute sul- 

 phuric acid is identical in composition with the black ob- 

 tained by boiling for two hours the deeper color of the lat- 

 ter being due to larger granules, which may be converted 

 into a brown powder, as he had previously shown was the 

 case with the black extract of natural humus. 28 C,Marc7i, 

 1873,185. 



CUEAgAO GUANO. 



In external characteristics the Curagao is very similar to 

 the Baker Island guano, which indicates a similar mode of 

 formation. It makes an easily divided, pulverulent mass, 

 containing coarser, pulverizable particles, with fine scattered 

 fragments of more or less decomposed coral. Under the mi- 

 croscope the powder exhibits white and brownish rounded 

 grains, often transparent, and seldom single, crystals of phos- 

 phate of magnesia and ammonia. Its chief ingredient is ba- 

 sic phosphate of lime, with a small amount of carbonate of 

 lime. Its reaction is slightly alkaline. Uric acid can not be 

 detected, the small quantity of nitrogen present being par- 

 tially in the form of organic matter, and partially consisting 

 of a very small amount of nitric acid. In the sample, taken 

 from the top layers, numerous remains of roots of grasses 



