186 Jlgricxdtural Geology of Onondaga County. [April, 



it will be profitable to pass in review some of the facts which 

 appear in these results. It will be observed, that lime and mag- 

 nesia are present in all the soils of this county. Yet neither are 

 present in that proportion w^hich many European agriculturists 

 consider a sufficient quantity; yet all the rocks are more or less cal- 

 careous, and some of them pure limestones. Still, even here, in 

 the soil which they bear, there is a decided defect, provided S or 

 9 per cent is a profitable dose. Some have considered magnesia 

 as injurious, and we believe this opinion has been maintained in 

 England and Scotland. The conflicting views in regard to its 

 effects seem to arise from the different effects which follow, where 

 it is in the form of a neutral carbonate, as it exists in the rocks 

 and soils, and those which follow from its use when applied in a 

 caustic state, as when a magnesian limestone is employed soon 

 after it is burned. Pure lime W'hen exposed to the air, air slacks 

 as it is termed, absorbs in the process both carbonic acid and 

 water. When, however, a limestone which is magnesian is thus 

 exposed, it remains in a caustic state for a long time, and in this 

 condition is decidedly injurious, or so long as it is caustic. This 

 fact, however, proves nothing against the value of magnesia in 

 husbandry, and besides we have direct evidence that it is neces- 

 sary to plants, from the fact too that it is obtained from the seeds of 

 plants by analysis. Perhaps we should not be justified in taking „ 

 the position, that the soils of the county are deficient in lime. 

 We believe, however, that many of the farms even in the limestone 

 district proper, will be benefitted by calcareous and magnesian com- 

 posts; and in making those composts, w-e would recommend the use 

 of the impure limestones, those especially which contain a large 

 amount of magnesia. A practice might be adopted in many 

 places of spreading the decomposing rocks and shales, which 

 crumble when wet: all of them, judging from their compo- 

 sition, will be found useful. Then, again, the marls and peat are 

 so abundant that calcareous and organic matter ought never to be 

 suffered to diminish to a minimum, or below 5 per cent. By the 

 practice of many of the ablest farmers, they keep a very steady per 

 centage, in the use of clover and plaster. Such, in fact, has 



