I. AGRICULTURE AND RURAL ECONOMY. 413 



phosphoric acid may have a corrosive action upon the plants. 

 It seems probable, however, that the trouble does not come 

 from the phosphoric acid at all, but rather from the sulpho- 

 cyanic acid in the sulphate of ammonia, which is often used 

 in the preparation of the so-called " ammoniated superphos- 

 phates." The sulphate of ammonia, which is made as a by- 

 product of the manufacture of coal-gas, and is largely used 

 for this purpose, often contains sulpho-cyanide of ammonia. 

 Investigations by a number of German experimenters indi- 

 cate that this works as a violent p.oison for vegetation. It 

 is well, therefore, to be sure that it is not present in am- 

 monia salts used as fertilizers. It is easily detected by the 

 red color which results from its solutions with those of salts 

 of peroxide of iron. 



KEEPING GRAPES FRESH. 



A method of preserving grapes for a long time, even from 

 one autumn until the next summer, has come into extensive 

 use. The grapes are kept on the vine as long as possible 

 in France, where this device originated, to the end of Octo- 

 ber or beginning of November. Before the first frosts ap- 

 pear they are cut, leaving a portion of the stem, of about two 

 or three knots below the bunch and two above it. The sec- 

 tion of the upper end is then to be covered with wax, to pre- 

 vent the evaporation of the liquids contained in the pores of 

 the wood ; and after carefully removing all the unsound 

 grapes the lower end of the stem is inserted in a small elon- 

 gated bottle filled with water, having a small quantity of 

 wood charcoal in the bottom. The space between the stem 

 and the tightly fitting cork through which it is inserted is to 

 be filled with wax. The bottles thus fitted are to be placed 

 on shelves in a dry room, and there arranged so as not to 

 fall over, this being best prevented by inserting them in holes 

 bored in a frame, as close together as they can stand conven- 

 iently. 1 J5, June 13, 1874, 173. 



EXPERIMENTS ON DIGESTIBILITY OF HAY BY SHEEP. 



In the experiment station at Hohenheim, in Germany, un- 

 der the direction of Dr. Von Wolff, a series of experiments 

 has lately been performed to determine the influence which 

 the addition of different kinds of beets and turnips to rations 



