Book II. 



LIME-KILNS. 



627 



585 ^^ ^ necessary (Jig. 585.) as well as advantageous, for more speedily 



and easily drawing out the lime. In some cases, instead of a 

 movable cover, a permanent roof of masonry (Jig. 586.) may be 

 adopted. This roof should have proper openings to admit the 

 supply of lime and fuel, and those may be closed by sliding shut- 

 ters or hinged doors ; while, in the roof, there should be a chim- 

 ney for the escape of the smoke. It will readily be understood, 

 that the use of a cover, whether fixed or movable, is chiefly to 

 retain the heat; but where the cover is a fixed structure, and 

 suflSciently large, something will be gained by placing the fuel 

 and limestones there, to be dried and heated before they are 

 thrown into the kiln. Three fifths of the contents of the Close, 

 burn oval kiln may be drawn out everyday, and when it is closed 

 at top and bottom, the fire will not go out for five or six days. 



38ti5. Subsequent improvements by Mr. Menteath are thus 

 detailed in a letter to us from that gentleman, dated Feb. 28. 

 1830. I now employ kilns of an egg shape, and also oval ; the 

 oval-shaped kilns are divided by arches across the kiln, descend- 

 ing four feet from the top ; the object of the arches across the 

 kilns is to prevent the sides of (he kiln falling in or contracting, 

 and also to enable you to form circular openings for feeding in 

 the stone and coal at the mouth of the kiln. Upon this plan, a kiln 

 of any length might be constructed with numerous round 

 mouths. In the model of the kiln lately sent to the Highland 

 Society, Booker's conical cover may be seen revolving upon an 

 iron ring placed upon the circular mouth, and having placed a 

 lid to the cover, I am enabled to prevent the escape of heat at 

 the top, and by cast-iron doors at the bottom the air is pre- 

 vented from passing through the kiln : so that by these precau- 

 tions the lime-burner can regulate the heat and prevent its escape 

 for several days, when the fire would be extinguished at this 

 season in the course of 24 hours. This is an object of great im- 

 portance, as it enables you to burn lime as well, and with as 

 small a quantity of fuel, in the winter as the summer season, and 

 to supply the farmer with as well burned lime, at any time of 

 the year, which cannot be done in the common construction of 

 kilns, open both at top and bottom. When coke is employed for 

 burning lime during the day, small coal should be used in the 

 evening, in order to prevent as much as possible the escape or 

 waste of heat during the night, from the rapid circulation of 

 air through the limestone in the kiln where coke is the fuel 

 made use of for its calcination : a kiln in which coke is the fuel 

 employed will yield near a third more burnt lime in a given time 

 than when coal is the fuel, so that coke may be used occasionally, 

 when a greater quantity of lime is required in a certain time, than usual, as it is well known to lime- 

 burners that the process of burning is done most economically when the kiln is in full action, so as 



almost constantly to have a column 

 of fire from the bottom to the top 

 of the kiln, with as short intervals 

 as possible in working the kiln. 

 Having found that limestone is apt 

 to be vitrified during the process of 

 calcination, during stormy weather, 

 from the increased circulation of 

 air through the kiln, which adds 

 much to the heat derived from the 

 fuel employed, and which experi- 

 enced lime-burners would have 

 diminished, could they be aware 

 at all times of an occurrence of 

 this kind. From having experi- 

 ence of the bad effects of too great 

 a circulation without properly pro- 

 viding against it, I have reason to 

 believe, that having a power to 

 throw in at pleasure an additional 

 quantity of air into the bottom of 

 a lime-kiln, that a considerable 

 saving of fuel necessary for the cal- 

 cination of lime would take place, and another object would be gained, that of cooling the limestone in 

 the bottom of the kiln, which frequently retards the drawing out of the burnt limestone for some hours, 

 or until the limestone is so cold as not to burn the wooden structure of carts. 



3866. hi uwking a kiln with narrow circular mouths, the stone and coal should be carefully measured, 

 so that the workmen can proportion the fuel employed to the quantity of stones ; and it is obvious, that 

 the quantity of coal to be used must depend upon its relative quality, and the hardness of the stone to De 

 burnt. If this measure were adopted in kilns of any construction, the lime shells would be found better 



3867. Two furnace doors are employed at the bottom of the kilns ; the upper one for '^tting through 

 the burnt shells [or stones] , which allows at all times thorough ingress of air into the DO"om ^t the ium, 

 and facilitates the drawing out of the lime, as it takes off" the pressure of the stone from top to "ottom ot 

 the kiln. The lower door is for drawing out the lime ashes, which is a clear gain to t^e lime-burner 

 In the long oval kiln, which admits of being made of any length, the eyes or fire-places are oPPos je to 

 each other, upon the two sides, which admits of a kiln being made ten or twelve feet wide -"^ bottom, 

 and enables the lime-burner to supply a very great demand from the kiln daily. C^ ix. btuart Mtnteain.) 



Ss 2 



