LIME. 



LIME. 



conclude that its employment was nearly as 

 extensive and as early as that of chalk or marl, 

 which were in very primitive times largely and 

 skilfully used for a similar purpose. Pliny 

 utests the use of it by the Roman cultivators 

 a dressing for the soil in which fruit trees 

 T ere planted. 



Of all the earthy manures found in England, 

 (ime is certainly the most powerful and rapid 

 in its effects on the soil ; and if its use is not 

 so extensive on the clays and peaty lands of 

 many districts of the island as is desirable, this 

 does not arise from the limited powers of this 

 earth, but rather from a variety of other causes, 

 such as its expense, the impurity of the lime 

 employed, and an ignorance of its most econo- 

 mical mode of application. 



The common varieties of lime used by the 

 English farmers, are procured by calcining 

 either chalk or limestone. Such lime is there- 

 fore rarely, if ever, chemically pure, for it 

 almost always contains a portion of silica 

 (flint), alumina (clay), and some red oxide of 

 iron. These, however, are not often present 

 in sufficient quantities to influence the fertiliz- 

 ing powers of the lime to any material extent, 

 as will be readily seen by the analysis of the 

 limestones and the chalk usually employed by 

 the limeburners. Common limestone is com- 

 posed of 



Parts. 



Carbonate of lime ... 95-05 



Water 1-68 



Silica 1-12 



Alumina 1-00 



Oxide of iron .... -75 



100- 



The slate-spar limestone contains 



Lime - 

 Carbonic acid 

 Silica - - 

 Oxide of iron 



- 54-70 



- 43-30 



- 0-55 



- 0-80 



- 0-65 



100- 



Common chalk is composed of 



Carbonic acid 

 Water 



united with various small proportions of the 

 other earths. There is also a very considera- 

 ble proportion of lime made in the north of 

 England from the magnesian limestone (called 

 by the Yorkshire farmers "hot lime"), all of 

 which differ considerably in composition ; that 

 from Sunderland contains, in 100 



Carbonate of lime 

 Carbonule of magnesia 

 Clay, water, &.c. 

 Oxide of iron 



Parti. 



- 56-80 



- 40-84 



- 200 



100- 



This "hot lime," which is well known by the 

 farmers in the neighbourhood of Doncaster, 

 and other parts of the north of England, can 

 only be applied in limited quantities, for the 

 calcined magnesia of the limestone remains 

 for a considerable period in its pure caustic 

 form, without absorbing carbonic acid gas 

 716 



from the atmosphere, and in this state its effect 

 is very pernicious to many kinds of plants. It 

 is only when pure, however, that magnesia is 

 prejudicial to vegetation : by exposure to the 

 atmosphere, it gradually and slowly absorbs 

 carbonic acid gas, becomes carbonate of mag- 

 nesia, and in this state forms a part of many 

 cultivated plants. Some of the most fertile 

 soils of Britain, in fact, contain it in this form, 

 in considerable quantities. 



Limestone occurs of various colours and 

 shades, as well as of different degrees of hard- 

 ness. In weight the compact varieties are 

 very much alike, being generally a little more 

 than 2 times (2-7) heavier than water. Lime- 

 stone may be distinguished from other varieties 

 of rock, by dropping on it some strong acid, 

 such as the acetic acid (vinegar), sulphuric (oil 

 of vitriol), or muriatic (spirit of salt), upon the 

 addition of either of which bubbles of gas are 

 observed to escape when lime is present, but 

 not otherwise. 



The action of the fire upon the chalk and 

 the limestones merely deprives them of their 

 water and carbonic acid gas, or fixed air. The 

 farmer must not fall into the very common 

 error of supposing that any thing is added by 

 the fire to the lime ; on the contrary, it loses 

 very materially in weight, by being deprived 

 of its carbonic acid gas, burnt or quick-lime 

 losing about 44 per cent, of its original weight, 

 a loss, however, which it gradually recovers 

 by exposure to the atmosphere, which always 

 contains this elastic vapour. 



One of the most remarkable properties of 

 quick-lime, is its tendency to combine with 

 water. If quick-lime be moistened with a 

 certain quantity of water, it soon becomes 

 heathed, throws off a portion of the water in 

 the form of steam, and falls to a very fine, 

 white powder, which is a hydrate of lime, al- 

 ways containing 24 per cent, water; if, how- 

 ever, more water be added, the same hydrate 

 is formed, but the excess of water agglutinates 

 the powder into lumps or masses which will 

 eventually become hard, and resemble stone. 

 Still more water immediately applied to quick- 

 lime, dissolves it, and forms lime-water. If 

 quick-lime be exposed to the air, it also falls to 

 a coarser powder by absorbing 12 per cent, of 

 water and 24 per cent, of carbonic acid from 

 the air, constituting a mingled carbonate and 

 hydrate of lime. The same change occurs 

 gradually with that which has been slacked by 

 water and is exposed to the air, the carbonic 

 acid of the atmosphere replacing the water of 

 the hydrate. The carbonate of lime, such as 

 exists in chalk, limestone, &c., is scarcely 

 soluble in pure water, but if the latter contain 

 carbonic acid, as rain water usually does when 

 in contact with the soil, the limestone enters 

 into solution. (Booth's Geology of Delaware.} 



The lime which I have used, observes Mr. 

 C. W. Johnson, has been principally made 

 from chalk, at an expense of about five pence 

 or six pence per bushel. That which I made 

 j from the magnesia limestone was from the 

 neighbourhood of Sunderland. This requires 

 less fuel to convert it into lime than the common 

 limestone. For the ordinary kinds, about one 

 bushel of coals is required for five or six 



