LIME. 



nefia : awi concludes, tliat, in general, the magnefian lime- 

 ftone may be eafilv diflinguilhed from the calcareous, by its 

 folutio^ in acids beitii; much flower, and that it contains 

 generally very few (hell? ; but that thcfe, when prefent, are 

 impregnated with magnelia. 



In the Philofophy of Agriculture it is remarked alfo, 

 that all lime-ftone may be divided into three kinds : firft, 

 the rocks which remain, where they were formed from (lieUs 

 beneath the ocean, except that they were afterwards ele- 

 vated by fub-marine fires ; fecondly, into alluvial lime-ftone, 

 as thofe which have been diftblved in water, and fimply pre- 

 cipitated, as the beds of chalk, which contain only the molt 

 infoluble remains of fea animals, as the teeth of Iharks ; and, 

 thirdly, thofe which, after having been diffblved and pre- 

 cipitated, have been long agitated beneath the fea, till the 

 particle? have been rolled fo againft each other, as to acquire 

 a (rlobular form, which is faid to refemble the roe or fpawn 

 of fiih, and which contain very few fhells, or none, as the 

 Ketton ftone, and that which he ha? feen on Lincoln heath, 

 extending almoft from Sleuford to Lincoln. Now, fays he, 

 as the falts of the fea confift of only two kinds ; common 

 fait, or muriat of foda, and vitriolated magnefia, commonly 

 called Epfom fait, %vhich, in the fea-waters furrounding this 

 idand, are found at a medium to exill in the proportion of 

 one-thirtieth part of common fait and one-eightieth part of 

 vitriolated magnefia, compared to the quantity of water ; 

 and, fecondly, as thefe falts are believed by many philo- 

 fophers to have been formed by vegetable and animal mat- 

 ters, which principally grew upon the furtace of the dry 

 land, after it was raifed out of the primeval ocean ; and 

 that, in confcquence, the faltnefs of the fea was pofterior 

 to the formation of the primeval rocks of lime-ftone ; we 

 may underftand why thofe lime-ftone ftrata, which have 

 not been diflolved or v.-aftied in fea-water fince the fea be- 

 came fait, are not mixed with magnefia. The chalk, he 

 fuppofes, muft hai-e been dinblvcd and precipitated from 

 water, as it exacllv refembles the internal part of fome cal- 

 careous ftalaftites which he has in his pofTefiion ; yet there 

 is no appearance *,of its component particles having been 

 rubbed together into fmall globules, and may not, there- 

 fore, have been removed from the fituation where it was 

 produced, except by its, elevation above the furface of the 

 ocean. But that alluvial lime-ftone, which confitts of fmall 

 globules adhering together, called Ketton lime-ftone, and 

 of which there appears to be a bed lo miles broad from 

 Beckingham to Sleaford in Lincolnfhire, and 20 miles long 

 fron Sleaford to Lincoln, he fulpefts may probably confill 

 of magnefian lime-ftone ; which is alfo faid in that country 

 to do no fervice to vegetation : tor this alluvial lime-ftone, 

 by having evidently been rolled together beneath the fea, by 

 v/hich the fmall cryftallized parts of it have had their angles 

 nibbed off, is moft likely to have thus been mixed with the 

 magnefia of the lea-water, which, as has been obferved, is 

 laid to contain one-eightieth part of its weight of vitriolated 

 magnefia. 



It is further remarked, that at the lime-works at Ticknal, 

 rear Derby, there appears a ftratum of alluvial lime-ftone, 

 like K.e;ton lime-ftone, which they do not burn for fale, 

 over the bed of the calcareous lime-ftone, which they get 

 from beneath the former, and calcine for fale. It is pro- 

 bable, he thinks, tkat the fuperior bed may contain mag- 

 nefia, which has rendered it not fo ufeful in agriculture. It 

 is ftlU more probable that alluvial Iime-ftone has acquired its 

 mixture of magnefia from the fea-water ; as magnefia, in its 

 uncalcined ftate, will precipitate lime from water, as ob- 

 served by Dr. Alilon, who thence propofes to render water 

 pure and potable, wliich has been long kept at fea free from 



putridity by having lime mixed with it, by precipitating" 

 the lime by the addition of mild magnefia. 



The lime from Brcedon is magnefian, that from Ticknal 

 (which is fold) is calcareous, he believes ; and fome farmers 

 in the vicinity of Derby affert, that two loads of Breedon 

 lime will go as far, that is, will apparently do as much fer- 

 vice to their land, as three loads of Ticknal lime. Breedon 

 lime, he is alfo informed, is preferred in architeiture, and 

 is faid to go further in making mortar ; which, he fuppofes, 

 means that it requires more fand to be mixed with it. In 

 the Account of the Agriculture of the Midland Counties, 

 lime made at Brcedon, near Derby, is faid to be deftruftive 

 to vegetables, when ulcd in large quantities ; and in Not- 

 tinghamftiire it is aflerted, that the iime from Critch, in 

 Derbyfliire, is fo mild, that thiftles and grafs fpring up 

 through the edges of large heaps of it, when laid in the 

 fields. Dr. Fenwick of Newcaitle obfervcs, that the farmers 

 in that country divide hme into hot and mild; whicii Mr. 

 Tennant believes to mean magnefian and calcareous lime. 



By experiments which were made by Mr. Tennaitt, by 

 fowing feeds of colevvort on various mixtures of calcined 

 magnefia with foil, and of calcareous lime with foil, he 

 found thirty or forty grains of lime did not retard the 

 growth of feeds more than three or four of calcined mag- 

 nefia : hence, what can we conclude, but that, as thev both 

 injure vegetation in large quantities, they may both affill 

 vegetation in fmall ones ? and that this is more probable, as 

 the farmers believe that they find both of them ufeful, 

 though in different quantities ; and as the magnefia would 

 form Epfom fait, if it met with vitriolic acid, which Dr. 

 Home found, from his experiments, to be friendly to vege- 

 tation, when ufed in very fmall quantities. More accurate 

 obfervations and experiments are, however. Dr. Darwin 

 thinks, wanting on this iubjeft. 



The moft certain way to know whether any fort of ftone 

 be fit for making lime is to drop upon it a little aquafortis, 

 fpirit of fea-falt, or oil of vitriol. All Hones on which the 

 above, or any other ifrong acid, eflervefces or rifes in bub- 

 bles, are calcareous Hones, or will burn to lime ; and the 

 ilronger the effervefcence is, the titter they are for that pur- 

 pofe. 



And as in the ufe of calcareous matter as a manure, much 

 depends upon its being brought into a fine powdery ftate, 

 it Ihould always, where fuel can be obtained at a moderate 

 expence, be prepared by burning, as that is the eafieil and 

 moft efficacious mode of reducing lime-ftone to powder that 

 ever was invented, and therefore ought always to be adopted 

 where neceffity does not prevent it. Reducing lime-ftone to 

 powder by calcination is alfo, he remarks, attended with this 

 farther advantage to the farmer, that it confiderably dimi- 

 nifhes his expence of carriage. Pure lime-ftone lofes about 

 two-thirds of its weight by being thoroughly burned ; fo that 

 the man who is obliged to drive this manure from a great 

 diftance, will find a very confiderable favingby driving it in 

 the ftate of ihells ; but if it were reduced to a powder by 

 mechanical 'rilure, he could not be benefited by this circum- 

 ffance. Many perfons choofe to drive lime-ftone from a 

 confiderable diftance and burn it at home ; but it is obvious 

 they then fubjedl themfelves to a very heavy charge in car- 

 riage, which would be avoided by an oppofite conduct. This, 

 therefore, ought never to be praftilcd but where other cir- 

 cumftances may counterbalance this unfavourable one. But 

 as lime-ftone is often in iti native ftate mixed with fand in 

 various proportions, and as fand lofes nothing of its weight 

 by calcination, it muft happen that thofe kinds of lime-ftone 

 which contain the largcft proportion of fand will lofe leaft 

 ill calcination, and of courie alford the weighticll lime-fhells. 



Hence 



