CHALDRON. 



CHALK. 



delphia, who enjoys a high reputation for his t 

 agricultural management, and especially for j 

 his success in feeding cattle, has returned to 

 the common old cutting-knife and box, so long 

 used by the German farmers in Pennsylvania, 

 an improvement of which is certainly a very 

 efficient implement. He says that he has ex- 

 pended much money for what were pronounced 

 the best patent straw-cutters, and finds it to his 

 advantage to lay them aside and return to the 

 old and simple machine, which costs but five 

 or six dollars. He had not seen the machine 

 invented by Mr. Bolts. 



CHALDRON. An English measure, contain- 

 ing 36 bushels, or 12 sacks of 3 bushels each. 



CHALK (Sax. cealc; Welsh, calck ; Celtic, 

 cal or kal). The carbonate of lime, or lime 

 united with carbonic acid. See LIME. Car- 

 bonate of lime exists abundantly in various 

 parts of the earth's surface in the state of 

 chalk, limestone, and marble ; and in smaller 

 masses, as the arragonite, &c., of which be- 

 tween one and two hundred varieties (all car- 

 bonate of lime) are knpwn to mineralogists. 

 For the purposes of agriculture they may be 

 all classed under one head. Common chalk 

 has a dull white colour, is soft, adhesive when 

 applied to the tongue, stains the fingers, and 

 thence is in common use for marking. In Eu- 

 ropean agriculture chalk is perhaps the most 

 extensively employed of the limestone species ; 

 it varies slightly in composition, containing 

 usually some silica (flint), alumina (clay), and 

 some red oxide of iron, and the remainder car- 

 bonate of lime, 100 parts of which contain, 



Carbonic acid 

 Lime 



Parts. 



45 

 55 



100 parts of common limestone are com- 

 posed, according to MM. Thenard and Biot, of 



Carbonate of lime 

 Water - 

 Silica - 

 Alumina 

 Oxide of iron 



Parts. 



- 95-05 



163 



1-13 



1- 



75 



100 



These carbonates, when burnt, form lime, 

 for the heat drives off the carbonic acid. By 

 exposure to the air the lime absorbs carbonic 

 acid gas, and again becomes converted into 

 carbonate of lime. A knowledge of these facts 

 is of considerable value to the farmer even on 

 the score of carriage, independent of the greater 

 value of lime as a manure ; for in some cases 

 the object of the needless weight of water and 

 carbonic acid in chalk is very material, as will 

 be readily seen by the following analysis of the 

 chalk of Kent, which is the variety largely em- 

 ployed in the county of Essex, although it has 

 to be brought by sea nearly 70 miles, and then 

 often carted several miles. I found by careful 

 experiment 100 parts of chalk from Kent, in the 

 state in which it was carted on the land in De- 

 cember, contained, besides some oxide of iron 

 and silica, 



Paris. 



. Water 24- 



* Carbonic acid 342 



tf Lime 41-8 



100 



310 



So that, when the farmer carts 41 tons of fresh 

 lime, he conveys as much real manure to his 

 soil as if he carried 100 tons of chalk. This 

 must be assuredly a question of the highest 

 importance to those farmers who have to carry 

 the earth a considerable distance, especially if 

 they can procure lime at a reasonable rate ; 

 which, in the large quantities required for agri- 

 cultural purposes, must in most situations be 

 the case. 



Carbonate of lime is found in almost all 

 vegetables ; it is an essential food of plants. 

 The cultivator will see, by the results of the 

 experiments which I shall give under the head 

 LIME, that the quantity of carbonate of lime 

 contained in the cultivated grasses is very con- 

 siderable, and still more so in trees ; and that, 

 as might be expected, the proportion increases 

 with the quantity of this substance found in the 

 soil. To the planter this fact offers an unan- 

 swerable reason in favour of the addition of 

 chalk, marl, or limestone to all poor soils in- 

 tended for plantations, in the manner long suc- 

 cessfully practised on the black heathy sands 

 of Norfolk by Mr. Withers of Holt, and which 

 he has shown to be equally advantageous to 

 trees, whether planted for ornamental or profit- 

 able purposes. 



There is no fact more necessary to be un- 

 derstood by the agriculturist, than that no land 

 can be productive which does not contain a 

 fair proportion of carbonate of lime. It is, 

 perhaps, even in excess much less prejudicial 

 to any cultivated soil than either silica or alu- 

 mina. But, on the other hand, no soil can be 

 productive if it contain more than nineteen 

 parts in twenty of chalk. The earth of the fine 

 sandy hop gardens near Tonbridge, in. Kent, 

 contain about five per cent, of chalk. The good 

 turnip soils near Holkham, in Norfolk, are 

 seven-eighths sand and the remaining eighth 

 is composed of 



Carbonate of lime or chalk 



Silica (flint) - 



Alumina (clay) - 



Oxide of iron - 



Vegetable and saline matter - 



Water 



100 



The soil at Sheffield Place, in Sussex, which 

 is so admirably adapted for the growth of the 

 oak, contains three per cent, of chalk. The 

 fine wheat soils of West Drayton, in Middle- 

 sex, contain more than ten per cent. That of 

 Bagshot Heath contains less than one per cent. 

 The richest soils on the banks of the Parret, in 

 Somersetshire, contain more than seventy per 

 cent. Those of the valley of Evesham about 

 six per cent. A specimen of a good soil from 

 Tiviotdale, examined by Davy, was composed 

 of five-sixths sand and the remainder of the 

 following substances (Lectures, 202) : 



Parts. 

 Clay 41 



Silica (flint) - 42 



Chalk 4 



Oxide of iron ------ 5 



Vegetable, animal, and saline matter - - 8 



A soil yielding excellent pasture, from the 

 banks of the Wiltshire Avon, near Salisbury, 

 yielded the same chemist one-eleventh of its 



