known, must be considered only as calcareous. The good effectsof gypsum (the sulphate of lime) are not yet experienced inScotland . All these containing calcareous matter combined, orthat soon must be combined, with carbonic acid, as stated in thelast section, may be taken in the group, and considered in oneview as calcareous : for though there be frequently a mixture ofextraneous matter, some notice of these mixtures may be takenafterwards ; anti we proceed to examine some of the propertiesof calcareous earth, as it operates On the soil.
Calcareous earth, or lime, as we shall henceforth call it, has, oflate times, been applied to the soil, in all quarters, to a greatextent, for the purpose of promoting fertility, and frequentlywith uncommon success. It is of vast importance therefore toknow something of those properties which have had such won-derful effects, and what has been the cause of failure where itsoperation has been less successful. But unfortunately our stock•of knowledge on this subject is very meagre, notwithstanding thelong and extensive use which has been made of it. The few fol-lowing are such of its traits as have been noticed, which are allwe have to enable us to judge of its effects in the soil.
Lime is extremely prone to combination, and never remains longin a simple state. Its affinity with carbonic acid is peculiarlystrong, taking this acid from its combination with other subtan-ces. In combination with some acids, it is soluble in water, but isoftener an insoluble compound.
In its simple or caustic state, it is said to dissolve in 680 timesits weight of water: but when this solution is exposed to the air,the lime forms a pellicle on the top, attracts carbonic acid, andprecipitates to the bottom, leaving the water sweet. In a shal-low vessel, this will take place in less than 24 hours: when quick-lime is mixed up with water, and spread very thin on a plainsurface, in the open air, it regains carbonic acid as quickly, andbecomes effete lime.
Lime takes in water, at all times, with great avidity, a greatpart of which it emits as freely. It holds, without dropping, a-Ibout half its own weight.
The dry powder of quick lime affects neither animal nor ve-getable substances. The hands of a person, who has wroughtin it all day, are not in the least injured ; and a rose immersedin it is more fresh, at the end of 24 hours, than if it had remain-ed in the open air. But when the lime has gotten water, the skinwith which it comes in contact is sodden, and the flower is blan-ched and disfigured. After the lime has become effete, it pro-duces no such effect, though it has been said to promote putre-faction. A handful of fresh straw was laid in one shallow ves-sel, with effete lime under, around, and over it; a handful wasput in another vessel, and surrounded in the same way with gar-den mould. Both were duly watered and kept always moist