362 Agricultural and Horticultural Chemistry. 



some of its most valuable products; some think that, by 

 exposing it a length of time previous to applying it to the 

 soil, they get rid of the sulphuretted hydrogen evolved 

 during its decay, which they consider poisonous to plants, 

 and many chemists, in preparing artificial manures, have 

 been very careful to exclude that substance, regarding it as 

 a poison ; but Mr. Solly has proved without doubt, by his 

 experiments, that its presence is desirable rather than oth- 

 erwise, when applied in limited quantity and with caution; 

 and in connection with this, Mr. Solly says: — 



"It is the custom in most parts of England to form the 

 manure intended to be used for the land into a heap, and 

 leave it exposed to the air for some time ; in certain coun- 

 ties in England and more particularly in the southwest, it 

 is a common practice to plant such manure heaps with 

 cabbages. These plants then grow in a soil rich in sulphu- 

 retted hydrogen and its compounds, and they are generally 

 very large and of a fine deep green color. They have, it 

 is said, a bad taste, and are only used for feeding cattle; 

 this bad taste has, however, nothing to do with the health 

 and vigor of the plant and involves another question. The 

 economy of such a system may be questionable, but it is 

 certain that the cabbages must absorb a large quantity of 

 ammonia and carbonic acid, and probably also of sulphu- 

 retted hydrogen, which, under the ordinary system of ex- 

 posing manure to the air, would be lost." 



" One of the substances of the greatest interest in vege- 

 table chemistry is sulphur. It occurs in the soil, the air, 

 in many vegetables, and in several of the best manures. 

 There are two compounds of sulphur with which we have 

 to deal in considering the influence it has on growing 

 plants, namely, that which it forms with oxygen, the sul- 

 phuric acid, and that which it forms with hydrogen, viz., 

 sulphuretted hydrogen or hydrosulpliuric acid. The for- 

 mer exists in the soil in combination with various bases 

 constituting sulphates; the latter is generated during the 

 decay or putrefaction of many organic substances, and is, 

 consequently, present in manure; it is also present, in very 

 minute quantity, in the air. The formation of this gas in 

 manures, «fcc. depends on the fact that sulphates or salts of 

 sulphuric acid are liable to be decomposed by decaying 

 organic matters, and hence those animal and vegetable 

 substances which contain sulphates frequently evolve sul- 



