OYSTER SHELLS. 



less often 1 with nitrogen, in all vegetable and 

 animal substances. It unites with various 

 bases, and forms alkalies, acids, and metallic 

 oxides. It is tasteless, and soluble in water, 

 which at a temperature of 60 absorbs about 

 ? V of its bulk. One hundred cubic inches of 

 this gas weigh about 34 grains. See GASES, 

 their Uses to Vegetation. 



OYSTER SHELLS. As a manure, the use 

 of crushed oyster shells has never been so 

 extensive in England as in Ireland ; and for 

 this neglect several causes have contributed. 

 They are composed principally of carbonate 

 of li'me, chalk, and a membranous substance ; 

 are in consequence not nearly so valuable as 

 crushed bones, which contain the phosphate 

 of lime ; are not to be obtained but at particu- 

 lar seasons of the year; and, unless pulverized, 

 are not sufficiently quick in their effects to en- 

 courage the farmer to use them unbroken. In 

 England they have been, therefore, little em- 

 ployed ; even in those districts, such as the clay 

 and sand formation, where, from the absence of 

 carbonate of lime in the soil, the calcareous mat- 

 ters of the oyster shells would be a very valua- 

 able addition. In Ireland, which is almost en- 

 tirely destitute of chalk, the use of the broken oys- 

 ter shells has been more considerable than in 

 England ; and in Dublin the parish authorities, 

 in hard seasons, are glad to set the paupers to 

 work to collect and break the shells which are 

 thrown away as rubbish ; and I am informed 

 that the money received for the powdered shells 

 affords a very tolerable remuneration for the 

 labour bestowed in their preparation. The 

 mother-of-pearl with which the oyster shells 

 are lined is similar in composition to the outer 

 shell or crust. This has been analyzed by M. 

 Merat Guillot, who found in 100 parts of mother- 

 of-pearl, 



Parts. 



Carbonate of lime (chalk) 66 



Membrane ------ 34 



100 



Powdered oyster shells should always, if 

 possible, be drilled in with the seed; for, by 

 thus coming into close contact with the plant, 

 all the volatile and earthy constituents of the 

 decomposing shell are absorbed by its roots 

 and leaves with the greater readiness, from 

 being placed more immediately in contact with 

 them. In this way they have been found to 

 answer very well on the light, sandy soils of 

 Norfolk, when drilled in with the turnip seed ; 

 as will be seen from the following account of 

 Mr. Blakie, in a letter to Sir John Sinclair, 

 dated Sept. 18, 1818: "Oyster shells pounded 

 or bruised (without having been burned) were 

 first used upon Mr. Coke's farm as a manure 

 in the year 1816. In the summer of that year, 

 the experiment was tried upon a hungry, Light, 

 sandy soil, which had been cleaned for turnips. 

 The oyster shell dust, or powder, was drilled 

 in the usual way, upon 27-inch ridges, at the 

 rate of 40 bushels per acre (without any other 

 manure), was slightly covered with earth, and 

 the turnip seed sown upon it. Another part 

 of the same field, quality of land equal, was 

 manured with farm-yard dung, at the rate of 

 8 tons per acre, put into the same sized ridges, 

 808 



OYSTER SHELLS. 



and sown with turnip seed as before described, 

 no other manure having been applied. The 

 turnips proved a good crop on both pieces: nor 

 was there any perceptible difference in the 

 bulk, but the produce was not weighed. The 

 turnips were all eaten upon the ground by 

 sheep; and the succeeding crop, barley, was 

 good on both, and apparently equal, but the 

 produce was not thrashed separate. The seeds 

 or layer crop of clover, in the present season, 

 1818, is a good plant, and appears equally so. 

 In this experiment, so far as it goes, it appears 

 that 40 bushels of oyster-shell powder are equal 

 in virtue as a manure to 8 tons of farm-yard 

 dung, at least for the purpose to which it was 

 applied. 



"In the autumn of 1816, powdered oyster 

 shells were tried as a manure for wheat, in 

 competition with rape-cake powdered. The 

 experiment was upon a one year's clover layer; 

 the wheat sown after one ploughing; the soil a 

 kind, light, gravelly loam. Oyster-shell pow- 

 der, at the rate of 4 cwt. per acre, was drilled 

 with the wheat seed on one part of the field ; 

 and on another part, of the same quality, rape- 

 cake dust was drilled with the wheat at the 

 same rate per acre as the shell powder; no 

 other manure was applied to either part. The 

 crop of wheat was good, nor was there any 

 perceptible difference upon the ground ; but the 

 produce was not thrashed separate. A similar 

 experiment was tried upon the same wheat 

 field, the manure applied at spring; the opera- 

 tion as follows: the wheat seed was sown without 

 any manure in the autumn of 1816, and in the. 

 spring of 1817 rape-cake dust, at the rate of 4 

 cwt. per acre, was drilled between the rows of 

 wheat ; at the same time an equal weight of 

 shell powder was applied in like manner to 

 another part of the field. The result of this 

 was similar to the autumn experiment, viz., 

 there did not appear to be any difference in the 

 crop produced upon the shell manure from 

 that on the rape cake. The field on which 

 these experiments were tried is now in tur- 

 nips, a good crop, and exhibits no difference 

 where the manure, as before stated, had been 

 applied for the wheat crop. These experi- 

 ments are satisfactory, so far as they go, but 

 certainly not conclusive ; because the produce 

 was in no one instance either weighed or mea- 

 sured. This I very much regret; but it appears 

 to be almost impossible to conduct such experi- 

 ments with a requisite degree of accuracy upon 

 a farm establishment of such magnitude as 

 that of Mr. Coke at this place. For, during the 

 hurry incident to collecting the harvest, the 

 farm manager has so many important concerns 

 to attend to, that he cannot devote any portion 

 of his time to superintending experimental 

 objects ; and were he to depute the manage- 

 ment of such concerns to the labourers, it is 

 not to be expected that they would pay the 

 attention requisite. The oyster shells are here 

 broken to pieces by passing them through the 

 oil-cake crusher; or are bruised by repeatedly 

 drawing a heavy iron roller over them when 

 spread upon a stone or hard-burned brick or 

 edge floor. I give it as an opinion, that oyster- 

 shell manure is likely to answer for gardens, 

 particularly to rake in with onions and other 



