438 



Farming of Herefordshire. 



the comstones are so abundant that scarcely any part of the central 

 districts of Herefordshire can be found where limekilns are not 

 numerous ; as previously remarked, however, these limestones 

 possess an earthy character, and are not considered so powerful 

 in producing fertility, especially on stiff' soils, as lime made from 

 the carboniferous or mountain limestone ; it is not uncommon, 

 therefore, to find the farmers sending for the latter, when at all 

 within convenient reach, in preference to employing that which 

 can be plentifully supplied in their own immediate vicinity. 

 The policy or impolicy of this plan will be discussed hereafter, 

 Avhen the general subject of liming is taken into consideration. 

 It may, however, be incidentally remarked that, according to the 

 texture of the soil, the mechanical action of earthy lime may be 

 advantageous or otherwise. Thus earthy lime may be found 

 more beneficial on silicious soils, owing to its adding aluminous 

 substances thereto, rather than the purer limes obtained from the 

 carboniferous limestones, whilst on a stiff' soil the latter may prove 

 most effective by rendering it slightly more open. The cohesive 

 tendency of argillaceous limestones has frequently been re- 

 marked : in fact, in degree, they are hydraulic or water-cement 

 stones. Thus, in Mr. DuncumlD's Report, it is stated, as the ob- 

 servation of a shrewd and observant farmer, " that lime ought to 

 be put on the land some days at least before the sowing takes 

 place, otherwise, in wheat crops, it will cause the ground to fer- 

 ment, and lie too closely round the seed during the winter ; or 

 in barley crops, it will prevent the growing of many of the grains 

 if hot weather immediately succeed the sowing." Although it 

 is not stated whether earthy or carboniferous lime is here alluded 

 to, the fair presumption is that the former is meant, as the action 

 is precisely such as might be anticipated, namely, the formation 

 of a hydrated double silicate or aluminate of lime, which, harden- 

 ing round the grain, prevented its growth. Although chemistry 

 was very little understood at the time the above was written, 

 namely, more than half a century ago, the true rationale did not 

 entirely escape that sagacious observer, Mr. Knight, who remarks 

 that the action of lime will depend much upon its quality. If it 

 be found to contain much flint and sand, and probably (when in 

 mortar it sets readily under water) some manganese,* Mr. Knight 

 observes, that it may be ploughed in hot, and immediately 

 before the sowing, even in large quantities, without injur}^ ; but 

 in other lime, and particularly in that which contains a propor- 

 tion of magnesia, more caution is necessary." Mr. Knight was 



This is an error of Mr. Knight's, as it is not manganese that gives the property 

 of mortar setting under water, but silica and alumina ; magnesia may also be pre- 

 sent. The remark of Mr. Knight, however, shows that the corustone lime was 

 meant. 



