CHALK. 



CHARCOAL. 



weight of siliceous sand. The remainder was 

 composed of 



Chalk 63 



Silica (flint) -------14 



y Vegetable, animal, and saline matter - - 14 

 Alumina (clay) ------ 7 



Oxide of iron 2 



Many soils also contain a small proportion 

 of carbonate of magnesia ; but it very rarely 

 amounts to a sufficient quantity to be worth 

 estimating in the mode of analysis I shall pre- 

 sently give. 



It is difficult to say in what form the carbo- 

 nate of lime enters the system of plants, as it 

 is an insoluble compound : unless we can sup- 

 pose that it attracts an excess of carbonic acid 

 from the air, becoming a bicarbonate, in which 

 state it is soluble in water. But whatever 

 may the cause of its being taken up by plants, 

 its influence on soils is undoubted. 



The mode of applying chalk as a manure. In 

 the county of Essex, where chalking is prac- 

 tised to a very large extent, the chalk is 

 brought in sailing barges from the Kentish 

 shore of the Thames, at an expense of about 

 two shillings per ton, and afterwards carted for 

 some miles into the country. It is applied in 

 quantities which vary from ten to thirty tons 

 per acre, according to the description of the 

 soil ; the poor light soils requiring a larger 

 addition of chalk than the richer lands. It is 

 usually applied without any preparation ; the 

 larger lumps of chalk are not even broken, and 

 the chalk being once ploughed in, the action 

 of the frost, the plough, and the harrow, in 

 time sufficiently pulverizes it. It is often 

 mixed in smaller proportions with common 

 farm-yard manure, ditch scrapings, pond mud, 

 &c., and suffered to remain some time before 

 it is carried into the field. An equally excel- 

 lent plan is followed by some of the best Essex 

 farmers, who spread quantities of chalk over 

 head lands, banks, &c., which require lower- 

 ing, and then fallow those portions of land, 

 ploughing them often, and letting the chalked 

 earth remain as long as possible, incorporating 

 before they carry and spread the mixed chalk 

 and earth on to the field ; by this means the 

 effects of a few loads of chalk are diffused over 

 a field. It is a plan admirably adapted for 

 those situations where chalk is very expen- 

 sive. 



The good effects of chalk are more perma- 

 nent than immediate ; for, although a good 

 dressing with chalk will remain in the soil for 

 from ten to twenty years, yet, on some soils, 

 one or even two years will elapse before the far- 

 mer perceives a decided improvement. There 

 is hardly any manure that answers better for 

 gr.ass than chalk, especially on light, sandy 

 soils. If, however, the soil already contains 

 an abundance of chalk, its addition to that 

 land cannot constitute a manure. The culti- 

 vator can easily fojyn a rough estimate of the 

 quantity of chalk in a soil, by taking a quantity 

 of it from three inches beneath the surface, 

 well drying it in an oven, and adding to, say 

 400 grains, 800 grains of muriatic acid ; the 

 mixture, which weighs 1200 grains, will, if it 

 contains chalk, effervesce ; and the carbonic 

 acid of the chalk being expelled, will, of 



course, lessen the weight of the mixture. 

 When the effervescence has entirely ceased, 

 weigh the mass ; every 4^ grains deficient the 

 experimenter may consider to indicate the pre- 

 sence of 10 grains of chalk in the soil. The 

 agriculturist will then be able to judge, by 

 comparing the quantity of chalk existing in 

 the examined soils with that in other lands, the 

 analyses of which I have given, whether his 

 land requires the addition of chalk. In the 

 United States chalk is nowhere found, and the 

 lime applied to agricultural purposes, except 

 it be in the form of gypsum or plaster of Paris, 

 is obtained from burning limestone, murble, 

 shells, either recent or fossil and lastly from 

 bones and calcareous deposits called marl. 

 (C. W. Johnson's work On Fertilizers, p. 256 ; 

 Brit. Farm. Mny. vol. iii. p. 129.) 



CHAMPIGNONS (Jgarints arcade*). A 

 species of mushroom, growing wild in Eng- 

 land, having a much' higher flavour than the 

 common mushroom, but tough and leathery 

 and consequently very indigestible. They are 

 chiefly used for making catsup, or in the form 

 of powder to flavour sauces, &c., for all which 

 purposes they are admirable. 



CHAR. A species of lake trout found in 

 Windermere; in length never exceeding fif- 

 teen or sixteen inches spotted like a trout, 

 with very few bones. (Wultun, p. 173.) It is 

 also found in Loch Tay, in Scothunl. 



CHARBON. The little black spot or mark 

 remaining after the large spot in the cavity of 

 the corner tooth of a horse is gone. 



CHARCOAL (From chark, to burn, and was 

 formerly written churke coal}. The remaining 

 portion of wood after it has been heated to red- 

 ness for some time, which dissipates all the 

 hydrogen and oxygen of which, with carbon, 

 it is composed. (See CAHBOX.) Charcoal- 

 burning is a regular trade, followed in some 

 of the woody districts by persons who da 

 hardly any thing else. 



For making gunpowder-charcoal, the lighter 

 woods, such as the willow, dogwood, and alder 

 answer best ; and in their carbonization care 

 should be taken to let the vapours freely 

 escape, especially towards the end of the ope- 

 ration, for when they are re-absorbed, they 

 greatly impair the combustibility of the char- 

 coal. 



By the common process of the forests, about 

 18 per cent, of the weight of the wood is ob- 

 tained; by the process of Foucauld about 24 

 per cent are obtained, with 20 of crude pyrolig- 

 neous acid of 10 degrees Baume. 



The charcoal of some woods contains silica, 

 and is therefore useful for polishing metals. 

 Being a bad conductor of heat, charcoal is em- 

 ployed sometimes in powder to encase small 

 furnaces and steam-pipes. It is not affected 

 by water ; and hence the extremities of char- 

 red stakes driven into moist grounds are not 

 liable to decomposition. In like manner casks 

 when charred inside preserve water much 

 better than common casks, because they fur- 

 nish no soluble matter for fermentation or for 

 food to animalcules. 



Lowitz discovered that wood charcoal re- 

 j moves offensive smells from animal and 

 I vegetable substances, and counteracts their 



311 



