THE OYSTER-INDUSTRY. 207 



Ou referring to tlio results of these analyses, we notice that the two samples of lime contain about 9 per cent, of sand and coal, or of 

 substances mostly derived from them, viz, oxide of iron, alumina, and silica. We have small quantities of potash, soda, magnesia, 

 phosphoric and sulphuric acids, altogether amounting to 1.5 j>er cent. Both samples contain also nearly equal quantities of earbouicacid, 

 ■viz, 8.3 per cent. Lime, the chief ingredient, varies from G4.5 to ."liJ.O, or nearly 11 per cent., and water from 17 to over 28, also 11 per 

 cent. Looking novr to the- statement of the proportions of the compounds probably existing in the samples, we see that in the two samples 

 of slacked lime the chief iugredieut is hydrate of lime (or calcium hydroxide) ; next to this in quantity comes carbonate of lime (or calcium 

 carbouate), fidlowed by silicate of lime 4.05 per cent., sulphate 1.03 per cent., and phosphate 0.4 i)er cent. 



The chemistry of lime manufacture. — A brief review of the chemistry of the lime manufacture may be serviceable. Clean 

 oyster-shells consist chietly of carbonate of lime. As they are used in lime manufacture they contain probably abont 7 per cent, moisture 

 and organic matter, about fi of soil and sand, and 87 per cent, of carbonate of lime. In passing through the kiln the carbonic acid is 

 mostly expelled. If completely expelled the loss would be 38 pounds of carbonic acid for 100 pounds of shells, leaving 49 pounds of 

 quicklime (calcium oxide). With this would of course remain the sand, mud, etc., that originally adhered to the shells, together with 

 the ashes of the coal used in burning. The lime thus obtained is slacked by throwing on water, in order to reduce it to a powder. 

 In this process of slacking, water and lime enter into chemical combination, the 49 parts of lime becoming 04 parts of hydrate of 

 lime. In practice some cavbonate of lime remains undecomposed by the burning, and, in the slacking process, the use of insufficient 

 water may leave some quicklime unconverted into hydrate, or excess of water may remain as moisture, as is the case with sample 329. 

 When applied to laud, oyster-shell lime may act as a fertilizer, strictly speaking, or as an amendment. Commonly, both kinds of action 

 are exerted, and the distinction between fertilizer and amendment is not generally recognized in i)ractice, although very important in 

 considering the effects of this substance. Lime is used as an amendment on heavy clay soils, two to three or more tons being sometimes 

 applied jier acre. On loams or light lands 1,000 pounds, or 20 bushels of oyster-shell lime, applied once in two or three years, is a usual 

 application, equivalent to the addition of 300 to 500 pounds to the acre annually. It is evident that the small quantities of potash, 

 nuignesia, au<l phosphoric acid contained in such doses of oyster-shell lime can have no sensible effect ui)on crops. It is the lime alone, 

 therefore, to which any benefit nuist be ascribed. A consideration of the modes of action of hydrate of lime, when applied as a fertilizer, 

 will make it evident that it is one of the most valuable aids to the farmer, and deserves more attent ion from Connecticut land-owners than 

 it has received. Our cultivated crops cont.ain, on the average, as much lime as i)Otash. The uecessity for the application of potash salts 

 is fully recognized, but probably the lack of lime is as common a cause of unfruitfulness ; for while jiotash seldom wastes from the soil to 

 any .serious extent, and is found in spring, well, and river waters in extremely small quantities, lime freely dissolves in water and 

 rapidly wastes from the soil, so that, other things being eqvial, there is more need for its restoration. 



Analysis of shell-makl and marine-mud. — Diverging slightly from this, Profes.sor Johnson analyzes in 

 the same report samples of shell-marl and mariue-iimd, which it was proposed to put on sale as manures, and it 

 seems worth while to quote the result of his important studies, as follows : 



The sample of shell-marl examined came from West Cornwall, and was found to be composed of — 



Moisture 23.92 



Silica, sand, and insoluble matter - 16. 88 



Oxide of hou aud alumina 1.55 * 



Lime 27.99 



Magnesia 0.97 



Sodii 0.59 



Potash trace. 



Sulphuric acid 0.46 



Phosphoric acixl trace. 



Carbonic acid 21.77 



Organic matters * by difference 5. 87 



100. 00 

 This shell-marl consists of carbonate of lime to the extent of 40 per cent., and contains 2 per cent, of carbonate of magnesia, also 

 0.9 per cent, of sulphate of soda, and 0.25 per cent, of carbonate of soda. The organic matter includes nearly 0.5 per cent, of nitrogen, 

 in organic comlnnation. There can be no doubt that its employment, in liberal quantities, viz, one^or more tons per acre, especially upon 

 grass lands, would often be attended with decided and long-continued benefit, but, in most cases, its action upon grain crops would not 

 appear at once in so decided a manner as is very commonly the case with good suj)erphosphates or guanos. 



The fertilizing eft'ects of this shell-marl, as well as its commercial value, may be safely measured by the percentage of lime which it 

 contains. Its eft'ects on crops would bo in general quite similar to those of oyster-shell lime, although somewhat less pronounced, since 

 carbouate is a less energetic agent than hydrate of lime. Its content of lime, 28 per cent., is less than one.half as much as that of the 

 two samples of slacked unscreened oyster-ishell lime described ou a previous Jiage, whose average is 59 per cent. As 1,C00 pounds of the 

 latter costs, at New Haven, shii)ped in casks, $3 20, it is evident that the proposed price of the marl, §15 jier ton, is much too large, even 

 after making the most liberal allowance for cost of handling. 



A sauiple of black mud, contaiuing some seaweed from salt water at Saybrook, was sent to the station by George M. Denison, esq., 

 who states that it is exi)osed at low tide, aud can bo got upon the land for about 25 cents per load. Chemical analysis assigned to it, of — 



Water 71.32 



t Organic and volati le matters 2. 79 



Sand, clay, aud sub.stauces insoluble in acid 20.82 



t Oxide of iron and alumina 2.62 



Lime 0.26 



Magnesia 0.52 



Soda 0.60 



Potash 0.17 



Chlorine 0.51 



Sulphuric acid 0. 39 



Phosphoric acid trace. 



100.00 

 " Containing organic nitrogen, 0. 44. t Contains nitrogen, 0.14 per cent. } Most of the iron exists as protoxide. 



